Crumbling leaves

This is my first grow, I started the flowering stage about 2 weeks ago. Both plants were in perfect condition, (so it seemed). The one in the back just started showing signs of the same thing even after I flushed them both. I am not really sure if this is a deficiency or a light burn, or maybe over feeding? I am using one, 100w led and two all red 90w led in a 4x2x5 tent. I am using fox-farm nutes. I noticed fox-farm nutes did not have any calcium. My ph remains around 7. I have an a-c unit so it never really gets too hot, I have a small fan circulating air. This began with just a few lower leaves the first week of flower, then spread rapidly during the next few days to the point of crumbling leaves, some looking rusty colored/spotted. My guess would be phosphorus or calcium deficiency so I added some vigoro (tomato and vegetable food plus calcium). I did not think to flush them before putting them into flower which could be a factor as well. Even though I flushed both, the one in the back broke out after the flush… I just want to know what I did wrong and how to salvage this/treat it so I can make sure this does not happen again.

Much appreciated,


The pH in soil should be around 6.0 - 6.5. Any higher and your plant will lockout nutrients.

Hopefully this chart will help. The range is different but I water at a 6.0 and the runoff is around 6.5 and I’ve had good results with it.

Actually bud soil should be around 6.3-6.8 but 6.5 being the sweet spot,

@pavala I’m going to go ahead and guess this is a calcium deficiency but its just my guess based off this chart here

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Thanks for the replies guys, I will adjust the ph and hope for new growth.


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No problem!

Happy Growing

This is the better spot to post this question, and the above advice is good. The pH might be contributing to nutrient deficiency problems. 6.5 is target pH for soil. If it is a soilless media you might need a lower pH. It is likely you need more calcium and phosphorus anyway, you will need more phosphorus and potassium in general during flower anyways. A flush before the transition to flower is not necessarily needed, unless you have a nutrient salt toxicity that has built up in your soil, but I doubt that was a problem here.

Happy growing,


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You need to fill out a support ticket. This way we could give you an informed answer instead of guessing.

Reason we need support ticket:

You did not mention method of growing: Soil, soil less, hydro???
PH 7.0 is neutral but on the high side for most optimum growing.

As mention 6.5 for soil is the tarhet
5.8 for hydro, and soil less mediums have to be experimented with in order to find the correct PH for Cannabis. After years of using ProMix BX I have concluded that PH should be 6.1-6.5 despite the website suggesting a PH of 5.5-5.8 This acidic of a solution does not work as well for Cannabis as does the higher almost soil target PH.

Hope this helps clarify why we need more information. If you are at 7.0 in hydro; That is the total issue, causing nutrient lockout. :slight_smile:
Happy growing

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Actually ProMix doesn’t recommend a pH of 5.5-5.8, they recommend a pH of of 5.8 to 6.2 for most plants, “General Plant Group”.

And they recommend a pH of 6.0 to 6.6 for the “Geranium Plant Group”. Or plants that are sensitive to Iron and Manganese toxicity if the pH goes down below its optimum level. And some plant species in this group also acidify the growing medium because the plants release acidifying ions, which cannabis does do, especially during flower.

Happy growing,


These were planted in foxfarm ocean forest. And yea I did notice the runoff to be a little too low around 5.5

Thanks MacG. I thought you guys posted the pH lower. My mistake. So my experimenting came up with basically the same PH as the company, after all. Cool

So; Now I am confused. This is what you called me on in the Labs. I posted to use 6.3-6.7 and you contradicted me. No argument here. Just find this curious. This is what I have been teaching all along.

Peace, lw :slight_smile:

Nope, I was commenting on a post where you said 6.8 was ideal in ProMix, but maybe it was a mistype, or other misunderstanding.

I’m glad we are on the same page and in agreement now.



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Have you used nutrients from thew start? If you did you most likely made the soil toxic by adding too much nitrogen, etc…

What exactly are you using from Foxfarm? You mentioned no Calcium in Foxfarm and that is not true. Grow Big has Calcium in it. 2.0% to be exact

Let us know.

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I had an autoflower do this and the other photo plants were fine

The conditions in each plant’s container can actually end up with different pH, even if you feel you are giving them all the same treatment.

Also, different strains, even among regular photo strains, maybe more so with auto strains, will be more or less sensitive to things like nutrient deficiencies, toxicities, or pH fluctuations.

So the fact that your auto was the only one that showed problems makes sense.

Happy growing,



Are they getting fresh air? It looks like slight nutrient burn, how often are you fertilizing? Organic or not organic? have you added any earthworm castings?

big bloom/tiger bloom, I used grow big for veg. I just measured my ph, it was at 4.5 so i think this is a lock up, am I wrong?