The beginning of a light burn or nute deficiency?

luxonator

luxonator

Active Member
I took a daily look at my remote surveillance feed and noticed this development on couple of leaves. I can't access the site in a few days to take a closer so wanted to ask your opinion about this.

This setup:
Barney's Farm Critical Kush, about a month into veg
4x4 tent
Full spectrum LEDs with ~500 PPFD at this time.
General hydroponics Aquafarm
Advanced Hydroponics of Holland nutes

Day temp/rh ~ 25-27C / 30-45%
Night temp/rh ~ 23-25C / 60-70%

Usually light burns/bleaching is more uniform and on bigger areas so I dunno if that is the culprit. Although if it's just starting I may see the bigger areas in a few days...

I'm using the same nutes I've used for decades so I dunno if this is a picky strain or if there is some other problems with the nutes. I've checked the PH and EC and they are normal.

Any opinion or input is appreciated.
what_is.jpg
 
I've raised the lights up a bit.
Raised the daytime humidity to around 60-70% RH
PH is ~6 and EC is ~1.4
Added some CalMag

Yellowing is still continuing and some brown spots starting to appear on the leaves. I really don't have a clue anymore what could be the problem. Gonna wait a couple of days to see if things start to get better, if not I'll do a full flush of the reservoir.
 
There is some paleness beginning ( between veins ) - however I would think a little pruning will in your future anyways.
 
I don't see things getting better. More leaves are starting to get rust spots and I don't see much if any of that healthy darkish green color.

I think I'll just flush the reservoir and start from a "clean slate". Only questions is, should I play it safe and give them say half the nutes as usually, or just the normal amount? I can't figure out if the problems are from getting too much or too little nutes.

I'm supposed to flip the light cycle within a week or two and defoliate some time later.
 

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If you were feeding full strength try 3 quarter, if you were feeding half try 3 quarter. If you were feeding ¾ go full strength... idk, how do the roots look? Do u have a good ph meter, kinda sounds like ph off and you don't know, have a root problem, or you dont have enough air.
 
ProPheT 216 said:
Do u have a good ph meter, kinda sounds like ph off and you don't know, have a root problem, or you dont have enough air.
Click to expand...

I've been using a drop ph tester. While it's not the most accurate tester, I know that the value is above 5.5 and under 6.5 and the closest color I get constantly is pointing to ~6. The nutes are stable and I've used more or less the same amount of ph down to get to that value for years. I test the solution before I add it to the system and the runoff water after the system has been cycling the water for a while. The ph seems stable.

The EC has been fluctuating more and few days ago when I tested the runoff water it was too high which I compensated by adding only half of the nutes, trying to keep the runoff water at EC 1.4. I don't have access to check the roots at this time. I try to do it when I flush the reservoir.

By "dont have enough air", do you mean ventilation or the O2 in the water? The system I use combines bubbles in the reservoir and a driptip from the top, so the water *should* be properly oxygenated.

aquafarm.jpg

blueberrymilkshake said:
Looks hungry. Does AN have calcium in it?
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I haven't found proper lists of what each of the 3-part nutrients have in them. I've been using Advanced Hydroponics Of Holland nutrients on hydro with good results for almost 20 years. I've added Calmag to my feeding schedule pre-emptively.

Haven't had these kinds of problems until I switched from HPS to LEDs so this makes me think these problems are due to either temperature or humidity or their combination (VPD). Although light stress might also be part of the problem, but I've tried to keep the PPFD on the lower side until the plants start to look healthier.
 
Last edited:
What problem?
Three marks on two leaves?
You can go chase anything you want …. but all you need is to up your feed a little bit.
 
drsaltzman said:
What problem?
Three marks on two leaves?
You can go chase anything you want …. but all you need is to up your feed a little bit.
Click to expand...
He mentioned only using HPS before now. This is his first time using LED. I'm guessing this is a learning curve thing because as far as I understood, lighting is the only variable.
 
drsaltzman said:
You can go chase anything you want …. but all you need is to up your feed a little bit.
Click to expand...
I'm hesitant to up the feed when the runoff water last time showed EC of 2.4, even when the max I've feed her during the veg has been 1.4-1.5. What could cause such a difference? Also, I can't really understand why the PH is so stable while the EC swings that much...

blueberrymilkshake said:
He mentioned only using HPS before now. This is his first time using LED. I'm guessing this is a learning curve thing because as far as I understood, lighting is the only variable.
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And as far as I understand, lighting affects the temperature and humidity (VPD) too due to the lack of IR on the LEDs. Ambient temps should be a tad bit higher so the leaf surface temperature gets to the same ballpark it was with HPS. Humidity changes with the airtemp (and vice versa) which affects the plants ability to transpirate etc.

Sigh, in hindsight it feels like HPS was way more simple system to run. Or maybe I'm just trying to optimize new areas now and need to re-learn stuff again.
 
What kind of light do you have? Mine has IR. In my tent, 82° (28ish Celsius) gets the best results. Temp appears to be more important than humidity (to an extent). And if you're run off is that high, I wouldn't increase till it's regulating the nutrients correctly either.

Hang in there, man.
 
blueberrymilkshake said:
What kind of light do you have? Mine has IR. In my tent, 82° (28ish Celsius) gets the best results. Temp appears to be more important than humidity (to an extent). And if you're run off is that high, I wouldn't increase till it's regulating the nutrients correctly either.
Hang in there, man.
Click to expand...

I have two SANlight EVO 4-120 lights. Currently dimmed to 60%.
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EVO 4-120 - sanlight.at

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Oo that's nice. I'm definitely going with too much light hahaha.

I have a ghetto light intensity test that has worked well for me so far. If my leaves are pointing upward, it's not too much. That only works if everything else is dialed in though.
 
Again what you said about ph, I have to adjust ph 2 times a day most the time, def at least once. If your not doing it daily thats def an issue.
 
ProPheT 216 said:
Again what you said about ph, I have to adjust ph 2 times a day most the time, def at least once. If your not doing it daily thats def an issue.
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Interesting. I thought that when I check the ph when I mix the nutes and later check the runoff and they are both fine I'll be good.
I will be investing in a quality PH pen tester to get more accurate readings and take them more frequently in the future then.
 
No you will have drift, to be lazy about explaining, everytime the plant uptake something it releases something, over time your + - charge will change, quite rapidly actually. Mine usually creeps up for about 4 days then creeps down for 2, day 7 I redo res
 
When I first changed from hps to led my plants showed the same thing. Not light stress but mild bleaching.
When you order your ph pen order a lux meter also. Takes the guess work out of it.
 
Update:

Looks like it was a nutrient lockout due to incorrect ph.

At first I tried to lower the EC and when it didn't work I tried to raise it as instructed by drsaltzman.

I monitored the progress for a week or so and the problems just continued and worsened so I bought a proper PH-pen. PH constantly dropped too low after refilling the reservoir (to around 5.2 at the time I need to refill).

I did a complete flush of the reservoir and started to feed them again with normal nute dosage. PH still dropped fast and too low so I started to give higher than normal ph water (~6.2). PH is "normal than usual" the day I fill the reservoir but will go down and settle on the desired range within 24 hours (drops to around 5.9 within the first day and then slowly goes to around 5.6 - 5.8 in the time when I need to refill)

New growth looks healthy, yellowing and brown spots no longer spread and stay on the old leaves.

I've been monitoring the situation for couple of weeks now and everything seems to going smoothly again. Healthy green growth. Both PH and EC stays in acceptable range now.

The ph-pen was really a worth while investment and a life saver. I just can't figure out why switching from HPS to LED caused these problems to manifest as I've used the same ph dropper test, nutes and hydro system for years without problem. I understand now that with the dropper tester had hard time to give precise idea on what the ph actually was as the different hues of orange that indicated ph 5 or ph 6 were really hard to differentiate.

Anyways, problem is now sorted and life goes on.

Special thanks to ProPheT 216 for guiding me on to the right track.
 
luxonator said:
Update:

Looks like it was a nutrient lockout due to incorrect ph.

At first I tried to lower the EC and when it didn't work I tried to raise it as instructed by drsaltzman.

I monitored the progress for a week or so and the problems just continued and worsened so I bought a proper PH-pen. PH constantly dropped too low after refilling the reservoir (to around 5.2 at the time I need to refill).

I did a complete flush of the reservoir and started to feed them again with normal nute dosage. PH still dropped fast and too low so I started to give higher than normal ph water (~6.2). PH is "normal than usual" the day I fill the reservoir but will go down and settle on the desired range within 24 hours (drops to around 5.9 within the first day and then slowly goes to around 5.6 - 5.8 in the time when I need to refill)

New growth looks healthy, yellowing and brown spots no longer spread and stay on the old leaves.

I've been monitoring the situation for couple of weeks now and everything seems to going smoothly again. Healthy green growth. Both PH and EC stays in acceptable range now.

The ph-pen was really a worth while investment and a life saver. I just can't figure out why switching from HPS to LED caused these problems to manifest as I've used the same ph dropper test, nutes and hydro system for years without problem. I understand now that with the dropper tester had hard time to give precise idea on what the ph actually was as the different hues of orange that indicated ph 5 or ph 6 were really hard to differentiate.

Anyways, problem is now sorted and life goes on.

Special thanks to ProPheT 216 for guiding me on to the right track.
Click to expand...
If you were looking at those colour pH strips under HPS you might get confused later under white LEDs. Its really nice of you, that you have come to update. Happy growing.
 
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