Leaves turn yellow, browns spots, get crunchy and fall.

So I have this recurring problem in my grows and it drives me nuts. I am starting to doubt my growing skills I have scoured the forums and I don't find many posts with problems exactly like mine. I research and research, look at of the deficiency charts, etc, and can't figure out the issue. It's weird because this has happened to me with multiple strains (autoflowers) in different mediums, (Promix before, now Ocean Forest). This has happened with my tap water, which is very hard, and is still happening with my reverse osmosis water that I am now using and adding calmag too.

-Soil: Ocean Forest with added perlite in Fabric Pots ( I added dolomite lime to this recent batch to make sure my soil wasn't getting acidic to see if that would solve the problem)
-Light: Mars TS3000 (about 14-20 inches above) on a 18/6 schedule
-4 X 4 Tent with sufficient exhaust fan
-Temperature ranges 74 - 82 F
-Humidity 60% during young veg, then down to 50%

I'm watering about every 4 - 5 days, when pot is light, and the lights first come on. I water slowly to ensure even saturation and I water just up to the point of runoff. I let the Ocean Forest feed the plants until they start to show the slightest signs they are hungry, then I do light feedings with Fox Farm Trio, but only Grow Big and Big Bloom. I do this every other watering. When I'm not feeding, I add calmag to my reverse osmosis water to get it up to about 150ppm. I always check PH with my nice Apera. I keep solutions to upper 6.5 - 7.0.

I have no pests whatsoever. I never see mold or mildew. I keep my tent clean and sanitary. Sometimes I've thought I had rust fungus but it never rubs off on my fingers.

The issues in these pictures always start when the plants start to slow down on vegetative growth and start building flower sites. It comes on quick and aggressive, and starts with the lower leaves and works up, taking out my fan leaves. It's always bottom to top. In my last batch, I did notice it seemed to be lower - mid growth, but where it was getting the most light. I usually live these problems all through flowering, and it always seems like I'm sliding/crashing across the finish line. I'm not sure how much it impacts my yields, but regardless, I want to nip this in the bud! No pun intended.

Always use the calmag, not just when you give it plain water.
And up your feed a bit, look like maybe some phosphorus along with calcium

When I used to use bagged soil, I would sometimes have similar problems.
I was always chasing this or that deficiency.
The only cure I ever found for soil mixes that come at various strengths was to compost the soil for a month before I used it.
Simply fill the pots, water them and let them sit on the sidelines of my grow.
I would water them like the flowering pots to keep them moist.
A month later I would plant starters in them to be ready when the current crop was done.
Seemed to do the best for me. I would still sometimes get odd problems, but they were never critical.
Now I construct all my soil, so have no recent experience.

First thought was excess calcium,added lime and your feeding calmag.Are the stems of affected leaves brittle?
Next would be what ppm do you feed? Do you feed to runoff?
Have you always used these nutes?

Have you tested the ph of your runoff? It looks to me like your soil is going acidic.

I'm seeing nitrogen, phosphorus, potassium, calcium, sulphur, magnesium, and molybdenum deficiencies all rolled into one. The fact that it's only effecting the older leaf's, has me puzzled.

How much dolomite did you add? FFOF uses oyster shells for pH buffering and that is very high in calcium plus the crab and shrimp meal in both have good amounts of calcium as well. Like @myke stated excess calcium is a possibility.

This study may have been done on vegetables but other plants and cannabis are going to suffer the same issues from excess calcium.

I think you have root aphid. Do the leaves feel thin and like paper? Rust streaks on the leaves? Buds feel thin and don't harden up? Check the roots, i bet they are mostly brown. The root damage will cause the same symptoms of nutrient deficiency.
Other possibilities- Calibrate your ph pen, or use drops to check your ph. Also, whats the nitrogen amount on your mix?

myke said:

First thought was excess calcium,added lime and your feeding calmag.Are the stems of affected leaves brittle?
Next would be what ppm do you feed? Do you feed to runoff?
Have you always used these nutes?

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I just looked into excess calcium. That seems quite possible. As far as the stems, once the leaves are pretty consumed, they just break from the stalk easily. Feed ppm usually comes out to around 700 - 800 I believe. Honestly, I haven't watched that so much ever since I started using RO water. I feed until water just starts to come out of the bottom of the pot, making sure the soil is fully saturated and its not just water running down the sides of dry soil. I have mostly used FF Trio. I have experimented with other nutes, had terrible luck, tossed them, went back to Fox Farm, and even a living soil mix. Similar issues with all.

xtsho said:

How much dolomite did you add? FFOF uses oyster shells for pH buffering and that is very high in calcium plus the crab and shrimp meal in both have good amounts of calcium as well. Like @myke stated excess calcium is a possibility.

This study may have been done on vegetables but other plants and cannabis are going to suffer the same issues from excess calcium.

Are You Sure You Need That Gypsum? Calcium Induced Deficiencies in Vegetables | Panhandle Agriculture

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I looked into that, I agree, it is definitely a possibility. I added one 1 tablespoon per gallon of soil. In my reading, I often came across people trashing the use of oyster shell in FF mixes, saying it didn't buffer efficiently, and that's why some people like to add the lime. Thanks for the link, I will read that shortly.

Plutonium said:

Have you tested the ph of your runoff? It looks to me like your soil is going acidic.

I'm seeing nitrogen, phosphorus, potassium, calcium, sulphur, magnesium, and molybdenum deficiencies all rolled into one. The fact that it's only effecting the older leaf's, has me puzzled.

Click to expand...

I have tested run-off recently, out of curiosity. On this plant it was about 5.8, which yes, is acidic. I have done a lot of reading of the efficacy of testing runoff and both sides make good arguments, but I'm not sure. My gut tells me that runoff will always come out a bit more acidic than the actual ph of the soil, so a runoff ph of 5.8 would actually be pretty good, suggesting the actual ph may be in the 6-7 range. Others mentioned calcium toxicity... which could lock out magnesium and potassium, according to what I have read. so that would explain multiple symptoms.

chex1111 said:

I think you have root aphid. Do the leaves feel thin and like paper? Rust streaks on the leaves? Buds feel thin and don't harden up? Check the roots, i bet they are mostly brown. The root damage will cause the same symptoms of nutrient deficiency.
Other possibilities- Calibrate your ph pen, or use drops to check your ph. Also, whats the nitrogen amount on your mix?

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Wouldn't I see some critters in the soil if I had root aphids? Also, how would I check what my roots look like? I always just see how much the roots have filled the pots at the end of my grows after harvest, haha. I have calibrated the pen a couple times. Sometimes when I am paranoid I even compare it to the results of my cheapo pen. They are pretty close together. Although I have always found it bizarre my RO water comes out with a ph of 8-9, just like my tap water. I know its purified though because the ppm is near zero. I was always under the impression RO is neutral, or acidic.

jcrunchy said:

I just looked into excess calcium. That seems quite possible. As far as the stems, once the leaves are pretty consumed, they just break from the stalk easily. Feed ppm usually comes out to around 700 - 800 I believe. Honestly, I haven't watched that so much ever since I started using RO water. I feed until water just starts to come out of the bottom of the pot, making sure the soil is fully saturated and its not just water running down the sides of dry soil. I have mostly used FF Trio. I have experimented with other nutes, had terrible luck, tossed them, went back to Fox Farm, and even a living soil mix. Similar issues with all.

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When the stems break off easily that means deficiency of Ca.Thats when they are still green though not all crispy.

myke said:

When the stems break off easily that means deficiency of Ca.Thats when they are still green though not all crispy.

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Okay nice to know that. Fortunately I haven't had them break off while green, only fairly crispy. I think I will do a flush with a very, very light feed when it is time to water, and assume I have excess calcium.