Help Diagnosing Micrgrow Leaf Issue

I wrote a few months ago as both plants - in my very restricted height microgrow (60cm x 40cm x 60cm) under an SF1000 100W light in compost and perlite, with pH adjusted water and Biobizz nutes - were losing leaves.

Fast forward to this grow. I still can't do anything about the size of my chamber and it is kind of fun but... I upgraded to Biobizz All Mix Soil, to go with their nutrients and kept the light to 60% brightness max, now 50%, at 24cm. Now I have got both plants to week 7 without much in the way of leaf problems apart from a little brown patch on one or two leaves of ONE of the plants.

The humidity in the grow room does vary between 35% - 55% which is a little low at worst, but there's little I can do apart from make sure I keep them watered and leave a moist sponge in there.

I've been using Biobizz nutes (Grow, Bloom, Topmax & Calmag) at 1/4 strength since week 3 - no pH adjustment, water pH appears to be around 7.2. I noticed a little rusty brown on one leaf - looked like potassium deficiency to me, but I'm likely wrong. I guess could have been light stress, but only on one plant and in the middle of the plant?

First 2 weeks, I only needed to water the plants once or twice, but have slowly increased this as they went into flower and now they are drinking ~500ml each a day.

In the last week or so, a few leaves have got brown patches and a couple have started twisting. Seemingly random locations on the plant and the other plant has no leaf damage apart from a little yellow brown at the tips. A few days ago, I wondered if I'd let the soil get too dry, it was dry down to about 7cm (the pot is only 14cm high but wide, to maximise the little height I have) but no leaves were wilting, just this dry leaf twisting on one or two fans? So maybe the twisting is a knock-on from there?

The nutes don't seem to have stopped the browning and the tips are yellow to brown, which I suspect means that even at 1/4 strength, I haven't watered the plants often enough that the soil is depleted enough to need nutes at even 1/4 strength?

I am including photos of both plants - though apart from slightly yellow leaf tips - only a few leaves, on one plant are affected currently. This has only occurred from about week 6.

I could imagine even at 50%, the 100W SF1000 at 24cm (less than the 12 inches closest for flowering at 100% power) might cause a little heat or light stress, though my hand is comfortable at leaf-top height and I don't want to turn down the light too far or prematurely as these plants only have another 3 or 4 weeks flowering to go. I will turn the light power down further, if light is the likely culprit though. I felt it looked like a potassium deficiency, hence continuing with the nutrients.

Any clues what the problem might be?

My opinion,
Looks to be a Cal/Mag/Potassium def./lock out

Potassium def will resemble Cal/Mag def but get miss categorized at times. Since you’re flowering, the Nutes that’s are being used will have higher levels of Phosphorus comparied to Vegging Nutes. Too much Phosphorus will lock out Cal/Mag along with further micro
nute’s if not corrected. Too much Cal/Mag will lock out Potassium. You’re kinda running in circles trying to correct it.

I would flush, and feed at a half rate of flowering Nutes for a feeding. Your growing in a Peet moss soil. I would treat the P.H levels around a 6.3 for that feeding. And see how she responds.

i would sugest ya all buy some seaweed liquid/solution and give at a rate of a single or half strength dose of this every week. its packed with micro nutes and trace elements like CALCIUM and MAGNESIUM as well as all the micro nutes and trace elements needed for growing cannabis and watering fresh water inbetween feeds to stop toxicity from over nuteing. this is for soil grows. co co grows can use the old folier feeding method of aplying the solution

Thanks guys.

A few questions / points, sorry to not get it fully yet!

I have been warned off pH correcting the water after my last adventure. You think it is worth doing even in All Mix soil?

I am using about 1/4 strength blooming nutrients at the moment. When you say half rate, do you mean half the rate I am feeding bloom nutrients, or double the dose so it is half the recommended?

Hearing your advice, I wondered if I shouldn't just sack off the Calmag and TopMax (fluvic acid & a touch of humic ) to make sure the potassium isn't being locked out and keep the bloom nutrients at 1/4 strength or even back it off to 1/8 strength?

Does that fit with your advice, or have I got the wrong end of the stick?

Cheers!

Midge

soil is verry forgiving when it comes to ph, it has a wide range of ph it will grow at, so you dont need to worry about testing ph unless theres an issue that cant be diagnosed. and fingers crossed thats not going to happen right
if you were making your own super soil, i wouldent bother with a ph test.
seaweed solution has its own feeding guide on the bottle, i would give this at half the sugested rate, once a week in place of a nutrient feeding, so instead of a food feeding, give the seaweed instead.

as for the problems your having, i would try giving plane water to your plant as jloi has allready stated. follow his instructions and see what happens.
theseaweed solution is a seperate thing all together.

sort one problem out b 4 you start with the seaweed, im just saying that seaweed solution has calcium and magnesium in it as well as plant growth stimulaters and other benaficial stuff.

so try out jloi's instructions and sort out the problem first, then after that, try useing the seaweed solution in place of a feeding once a week at half strength

Ok, cheers for the advice.

allways sort one problem out befor you start adding anything else that may make the problem worse,

I totally agree, I just dont know if Jloi meant give them half the recommended dose after flushing or half the dose of nutrients that I have been giving them.

I've been giving them:

1ml / 5L BBGrow(veg) (1/4 recommended strength)
4ml / 5L BBBloom (1/4 recommended strength)

Does Jloi mean to give them:

0.5ml / 4.5L BBG (~1/8 recommended strength)
2ml / 4.5 BBB (~1/8 recommended strength)

or

just 8ml / 5L BBBloom (1/2 recommended strength)

Also go go kid: I have some liquid seaweed coming. If I end up using that, is it in addition to bloom nutrients or in place of them? I guess I can read the label when it comes, but interested in your take as you are already a user of the stuff and so you might have an opinion on that.

Thanks again for your suggestions and patience

Midge

i would say yes, keep it on the low side, you can allways add more but you cant take it away, to be safe, feed
0.5ml / 4.5L BBG (~1/8 recommended strength)
2ml / 4.5 BBB (~1/8 recommended strength)
unless he posts other wise.
you can allwatys reply to his post with the question, that way he will be allerted to your question and correct me if im wrong

the seaweed solution is in place of a feed, it contains potassium and phosphorus as well as all the micro nutrients and trace elements, so its like giving it a bloom feed with extras.
BUT SORT YOUR ORIGINAL PROBLEM OUT FIRST, BEFORE APLYING ANY SEAWEED

go go kid said:

i would say yes, keep it on the low side, you can allways add more but you cant take it away, to be safe, feed
0.5ml / 4.5L BBG (~1/8 recommended strength)
2ml / 4.5 BBB (~1/8 recommended strength)
unless he posts other wise.
you can allwatys reply to his post with the question, that way he will be allerted to your question and correct me if im wrong

the seaweed solution is in place of a feed, it contains potassium and phosphorus as well as all the micro nutrients and trace elements, so its like giving it a bloom feed with extras.
BUT SORT YOUR ORIGINAL PROBLEM OUT FIRST, BEFORE APLYING ANY SEAWEED

Click to expand...

Brilliant, thank you go go kid and a good suggestion, my brain has slumped lately!

@Jloi could you chip in and clarify if you meant half the dose I am giving them currently, or half manufacturer's recommended dose please?

Thanks both for the help and support, it is very much appreciated!

Midge

Jloi said:

My opinion,
Looks to be a Cal/Mag/Potassium def./lock out

Potassium def will resemble Cal/Mag def but get miss categorized at times. Since you’re flowering, the Nutes that’s are being used will have higher levels of Phosphorus comparied to Vegging Nutes. Too much Phosphorus will lock out Cal/Mag along with further micro
nute’s if not corrected. Too much Cal/Mag will lock out Potassium. You’re kinda running in circles trying to correct it.

I would flush, and feed at a half rate of flowering Nutes for a feeding. Your growing in a Peet moss soil. I would treat the P.H levels around a 6.3 for that feeding. And see how she responds.

Click to expand...

just in case midgesmith's call did not get to you, hes concerned about your answer. many thanx

Thanks! I figured the @ his name would work in the same way, though I could be wrong about that too @go go kid

I'll get everything right one day. By the law of bloody averages it must be true