Leaf necrosis - expert help needed

I have the attached leaf necrosis. I am using ebb and flow with 8'' Rockwool slabs under HLG Quantums (3k color). This is my first grow with these lights. I noticed some leaf necrosis on only *some* of my plants, I have 30 plants on this 8x4, all the same strain (Blue Cheese Dynafem) but 3-5 different phenos from the different beans I popped. It looks like it starts around the bottom to middle of the plant and starts to work it's way up. I was thinking magnesium, but I have been using CalMag at 4ml/litre (0.4-0.5EC - bit high since I read deficiency happens with Quantum boards) since the start of the grow. I check and PH every day @ ~6.0. My water is RO + calmag and nutes, and Hydroguard. Right now I just flipped to 12/12 and my EC is 1.7 although I might up that to 1.8. I checked the roots coming out of the rockwool slab and they are white as can be, so it doesn't look like root rot.

It's so odd it only is affecting some of my plants. I have been doing runs on this table with many different strains, no issue like this before, the only change is from HPS to Quantum lights. I tried upping nutes but it doesn't seem to have helped and I don't want to toxify the root zone. At a loss, appreciate any help if you have seen this before. Could it be a fungus or disease? Temps are between 65-85 nigh/day and humidity is kept around 40%. I only flood the table once per day.

Hey mate.

I havnt dabbled in ebb n flow before, so I'm making a few assumption about your table. I'll list them as questions.

I understand ebb fills from the bottom. Then drains?
How does yours fill, then drain? From the middle, end to end etc, etc.
The plants that are affected. Are they together on the table?
Is the problem area isolated?
What medium are you using for your table? Rockwool, Pearlite etc. Or none?
What are your reservoir temps?
Is there any slime building, on the edges of your reservoir? Can you feel any?
Has this problem been getting worse since the added calmag?? The orange spotting in the leaves makes me wonder.
Another thought is the problem plants are right where it's filling and draining?

My table fills from the middle and drains there too from a mushroom siphon valve, but like I said in my post I have done multiple runs so it doesn't seem to me like a setup issue. I run Rockwool, and I don't have slime in my reservoir because I use HydroGuard which is a beneficial bacteria. I checked and did not see root rot, rather sparkling white roots actually. I also run a high powered pump in my res 24/7 to keep it moving and mixed.

The problem initially seemed to get better when I upped the Calmag, then it came back same as before on the same plants but hasn't spread to other plants. And the plants are all over the table, not in one spot, and not limited to only one phenotype. Res temps are in range 62-72.

I wondered too if it could be excess iron from the CalMag, but per what I just said it makes no sense that it showed up at only 2ml/liter and then I upped it to 4/ml per litre and it went away and then came back. I am going to hit with a foliar spray in the dark period twice a day for the next week and see what happens since I am out of any other ideas I guess. One idea I had if it was a fungus was to create some really highly ozonated (O3) water and spray with that. I will try that if foliar feeding does nothing.

Pic of the plant more useful than a dead leaf pic.

Bugeye said:

Pic of the plant more useful than a dead leaf pic.

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I literally just picked those leaves 2 mins before posting so I could take the pic in natural light. I'll go take one in the room though.

HotKarl2 said:

I literally just picked those leaves 2 mins before posting so I could take the pic in natural light. I'll go take one in the room though.

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Trust me, you will get better advice by showing the plant.

Sure ain't starving her. Might give the blocks a good washing. Knock the salts off.

Jypsy Dog said:

Sure ain't starving her. Might give the blocks a good washing. Knock the salts off.

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The problem first showed up at 1.0EC with only 0.3EC base Calmag& RO. So not exactly overfeeding when I first saw it. Same problem now @1.7 EC, but plant looks healthy otherwise. I have heard from running HLG QBs that you need more calmag and more fee also..

Bugeye said:

Trust me, you will get better advice by showing the plant.

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Ok here are four pics I just took in the room. I adjusted for white balance on one, and the rest are auto (my light spectrum is 3k). You can see the mostly healthy plant, and my hand holding the middle of plant affected leaf. The last pic is my mostly healthy table. This damaged leaf is getting light, it is not in the shade, nor are the other damaged leaves on the other plants.

Mate I'm gonna go out on a limb.
I think cut your calmag.
Don't change your base nutes. Leave them the same.
See if it keeps spreading.
It ain't gonna all drop dead from deficiency.

They really don't look deficient in anything.

Have you been letting your reservoir creep a little over 6 before changing or topping off?
Are you getting healthy swings in ph?

If you're ph is low all the time, it locks out calcium and magnesium.
If ph is high, it locks out iron.
Is your ph swinging between each, to get everything?

Seems like a magnesium issue, and seems it may be a little locked out since you are providing it. So if ph is good, I'd wonder if too much calcium may be blocking it? Can't say I have grown under your new lights but wondering if you got good advice on needing to raise cal/mag levels?

Yeah, I let it swing between 5.7 and 6.2 but try and keep it in the range of 5.9-6.0 . I always let the plants tell me when the nutes are too much or too little based on how the reservoir reads after a feeding.


I hate to disagree but I am thinking it is a virus or fungus or a VOC or other element from my well. I appreciate your advice though, it's solid for a newer grower. I'm not a new grower however, so I think the basics are already covered. My symptoms don't correlate with this either, except for excess potassium, which I know is not the case. One thing is my well water could have some organic VOC that is passing through all my filtration and only occurs now due to whatever. I am thinking as well as an ozone wash to kill fungi, I might ozonate my next reservoir at res change using a venturi effect to dislodge any soluble elements and then filter with charcoal. Even though my PPMs come out 0 from the DI after RO, organic elements could still be saturated in solution for example manganese, although I have dealt with excess saturated manganese before and it does not cause this specific necrosis, it is well documented in the pic above actually.

But mainly, I posted the thread because it would help me to diagnose the issue if anyone has seen similar leaf necrosis?

Bugeye said:

Seems like a magnesium issue, and seems it may be a little locked out since you are providing it. So if ph is good, I'd wonder if too much calcium may be blocking it? Can't say I have grown under your new lights but wondering if you got good advice on needing to raise cal/mag levels?

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It's all over RIU with regards to HLG QBs. But in addition the issue happened at low EC, so I needed to raise EC anyways.

If your ph has been in range. Judging by your ec's, you shouldn't be very deficient in anything.
More likely too much of something, or a few things.
If anything later maybe up you base nutes.
IMHO
I think the black is excess nitrogen, and the spotting is excess calcium. The yellow between the vains, is either iron or mag.
You have been supplementing plenty. It's balance that the plants don't have. There has to be too much of something.

Something fungal is a possibility. But I'd make sure it isn't what you're feeding first.

Tim1987 said:

If your ph has been in range. Judging by your ec's, you shouldn't be very deficient in anything.
More likely too much of something, or a few things.
If anything later maybe up you base nutes.
IMHO
I think the black is excess nitrogen, and the spotting is excess calcium. The yellow between the vains, is either iron or mag.
You have been supplementing plenty. It's balance that the plants don't have. There has to be too much of something.

Something fungal is a possibility. But I'd make sure it isn't what you're feeding first.

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Well I have used the same feed on the last 10 strains, which all did really well. I upped the calmag only by 0.1-0.2 EC due to the intensity of the new LEDs, which is not much uppage at all. If it was excess Nitrogen I would expect to see more downward clawing of the fans, of which I am seeing like close to zero.

However having dealt with well water problems before, I am somewhat inclined to suspect VOCs too. I had excess manganese which no one could help me solve, I figured it out myself using the pic above, and then research helped me discover o3 could remove it. Maybe there is a VOC in my seasonal well water that passes through RO & DI filtration.

Anyways if it is fungal it will worsen when I foliar feed at night. If it stays the same/gets better it isn't fungal.

Thing is though calcium can blacken the tips too.
It's happened to myself before. I way overlimed my garden. Tips and edges were dark and mushy like I had rot.
I'm not sure nitrogen is what you have excess of. Because as you say, there is no clawing.
But I believe it's more of an antagonist of your symptoms. As you probably already. Know it's why they put nitrogen in calmag. Nitrogen is the antagonist that helps bind the calcium, magnesium and iron. To make it available.
If your plants have an imbalance of micros. Adding calmag is making it better briefly. Because the calmag is instantly available.
But once your table drains, and you're left with calcium etc, in your Rockwool..........

It can't possibly be your light. The plants can't be absorbing that much extra energy. Are they much bigger than the last, at the same age?
Calmag is the one thing besides your light that's changed from previous grows.
If your environment has been fine. Calmag seems like a mighty big elephant, in a tiny room.

Tim1987 said:

Thing is though calcium can blacken the tips too.
It's happened to myself before. I way overlimed my garden. Tips and edges were dark and mushy like I had rot.
I'm not sure nitrogen is what you have excess of. Because as you say, there is no clawing.
But I believe it's more of an antagonist of your symptoms. As you probably already. Know it's why they put nitrogen in calmag. Nitrogen is the antagonist that helps bind the calcium, magnesium and iron. To make it available.
If your plants have an imbalance of micros. Adding calmag is making it better briefly. Because the calmag is instantly available.
But once your table drains, and you're left with calcium etc, in your Rockwool..........

It can't possibly be your light. The plants can't be absorbing that much extra energy. Are they much bigger than the last, at the same age?
Calmag is the one thing besides your light that's changed from previous grows.
If your environment has been fine. Calmag seems like a mighty big elephant, in a tiny room.

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Calmag has only changed by 0.1-0.2 EC not enough to do what happened. Think about it! 0.1 -0.2 EC? Thtat's only 50-100ppm on the 50 scale.

However, one thing did happen that I am thinking about. My pre RO KDF filter and my post RO, DI filter both failed. And my res had that water from the start when I put clones on the table. My post RO probe was only reading 3 TDS so probably not a big failure but that would be just salt from my water softener then that might be enough to cause the black death necrosis? The problem has stayed with me since filter and res changes though, makes me think it is a VOC soluble in solution passing through filters.

I think you'll find calcium is your culprit according to your supplied chart too. It has black tips too.
Calcium attaches to itself as well, just like a bone. That's why I'm suspecting it's calcium. Because there may be a lot more in your Rockwool than you realise. Magnesium and iron will generally flow straight through. Calcium won't nearly as much.
I'd bare it in mind man. I'm way suspect on calcium buildup in your rockwool.

Take it easy.
Hope you find your problem

Tim1987 said:

I think you'll find calcium is your culprit according to your supplied chart too. It has black tips too.
Calcium attaches to itself as well, just like a bone. That's why I'm suspecting it's calcium. Because there may be a lot more in your Rockwool than you realise. Magnesium and iron will generally flow straight through. Calcium won't nearly as much.
I'd bare it in mind man. I'm way suspect on calcium buildup in your rockwool.

Take it easy.
Hope you find your problem

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Thanks man, but not everything is a Calmag problem unfortunately. When all you have is a hammer though, everything does tend to look like a nail.

A flush just seems way out of line given the problem presented with low nutes as well. If I had flushed them then they would have died from starvation.

I'm sorry but I respectfully disagree. Calmag is essential, and is the first to show itself before anything, besides nitrogen. Deficiency or toxicity. Calcium and magnesium should almost be included in npk. But they're not. Because whether we like it or not, they're still micros.
You have come here asking for advice.
A mighty big hammer unfortunately is all you are gonna get as advice.
Seems you would be better finding the cause yourself, and posting the results in a week or two.
As I previously stated. It may be as simple as upping your npk, and lowering your calmag. I don't believe I said the word flush.

Just take it easy. Maybe someone else has a better suggestion.
Hope you find your cause.