Yellow leaves

[Timmeeeh]

Hello folks, I'm chasing my tail trying to figure out the cause of my yellowing leaves. This is my 5th grow. Fifth generation clones of Dutch Passion Power Plant. My substrate: coco coir, homemade compost, homemade worm humus, perlite, vermiculite. Tap water ph is over 7.5, which I adjust down to 6.5 and let sit a full week or longer before watering.

My plants veg very nicely, but somewhere around week 3 of flowering, as the new buds begin to explode, my fan leaves begin to yellow. I'm now at the start of week 7 and the yellowing is beginning to really look disheartening.

I feel it's important to mention that the yellow leaves DO NOT shrivel up, die and fall off the plant. I tend to remove them by hand, but they require a significant "tug" before coming free. I also believe that this particular "species" simply has a lighter/brighter green color than most.

It's also important to add that the quality of the end-product is really quite satisfying.

In any event, Google seems to pinpoint my problem as, either:

• Overwatering
• Underwatering
• pH lockout
• Light stress
• Nutrient burn
• Nutrient lockout
• Or simply, normal function of the plant cannabolizing itself before harvest

Can any of you look at my pictures and give an educated guess as to what may be going on?

In the past, I've had problems with overwatering, but if anything, I may now be over-correcting and underwatering. But at no point in time have I ever seen the plants looking wilted, whatsoever.

I'm conscious of always adjusting pH to 6.3 - 6.5

If anything, my SF2000 pro is slightly undersized for my 30"x30" tent. This run, I've dialed the light back to 80% and keep it a full 2 feet above the canopy.

Temp is max 78°F (lights on) and min 65°F (lights off)
RH 50% - 60%

As for nutrients, I water with vericompost tea, bubbled for 24 hours with a dose of molasses.
2 or 3 days later, I water with straight water.
2 or 3 days later I water with BioBizz according to their "light mix" scedule.
2 or 3 days later, plain water.
2 or 3 days later I repeat the cycle with a batch of vericompost tea.
I try to limit my runoff as much as possible.

My next run, I would like to give each pot it's own unique watering/nutrient schedule. It will be a complete pain in the a**, but I'm willing to do it, if it can fine tune my grow for the future.

But perhaps one or more of you already have experience with this scenario and can save me the aggravation. Or offer suggestions as to how I can best proceed with pinpointing the problem

Thank you, in advance

Greeting from southern Germany

[Lizard]

Your plants look good, yellow leaves are a natural progression some more than others . Nice grow. I don't use coco but I think 6.3-6.5 is a tad low. Some nutrients lose the ability for intake at 6.2. I keep my runoff at 6.5 feed at 6.8 with soil. Just like this.

[Gator]

Looks like a calcium and magnesium deficiency to me

[Lizard]

Looks like a calcium and magnesium deficiency to me

Good call Gator. That would be first on my list but there at 7 weeks. Question is did you buffer your coco and do you feed calmag I presumed you did.

[Timmeeeh]

Thanks Lizard. I'm confident you've set me on the right track.

[Timmeeeh]

Woah! Did I buffer my coco?!? (exploding head emoji)

I thought I've read everything there was to know about soilless substrate, but I missed the part about buffering the coco with calmag. I'll get right on researching that.

Would you happen to know this answer:? Since I've already mixed several dozen gallons of soilless, is it too late to buffer? Or can I simply soak the entire mix of compost, perlite and all?

Also, does it make sense that a calmag deficiency wouldn't manifest itself earlier, during veg?

[golfnrl]

Some brands of coco come prebuffered. I've used them without issue. Some coco does not come pre-buffered. You can dose with cal/mag most any time. Yes, the timing makes sense.

[Lizard]

Woah! Did I buffer my coco?!? (exploding head emoji)

I thought I've read everything there was to know about soilless substrate, but I missed the part about buffering the coco with calmag. I'll get right on researching that.

Would you happen to know this answer:? Since I've already mixed several dozen gallons of soilless, is it too late to buffer? Or can I simply soak the entire mix of compost, perlite and all?

Also, does it make sense that a calmag deficiency wouldn't manifest itself earlier, during veg?

There are receptors in coco that suck up cal and mag you buffer it with calmag to keep them full leaving the rest for the plant. You also keep up treatment with calmag. How much I don't recall offhand, I use soil. Someone here with better knowledge will surely help you if not google buffering coco and you will find the info.

[Lizard]

Overall your plants look fine for 7 weeks, not long to go they'll be fine with no intervention. If it makes you happy feed them a little calmag, but next time around buffer and feed them. I went to kindergarten in Dusseldorf Germany.

[Timmeeeh]

Vielen herzlichen Dank nochmal, Lizard.

I'll be surfing the web quite intensely. If I have any more questions specific to calmag/coco buffering, I'll open a new thread. This thread got kinda long-winded. (I blame it on the Ohio catholic school education.)

[Rwise]

Raise the PH to 6.5-6.8 and add calmag, the girls are eating there leaves for the nutes in them. I would call your media soil/soil less mix

[Allotrope1000]

Hey, Timmeeh!
Lots of good advice from experienced growers to your concerns. Let me offer one more thing.
Check out the "cocoforcannabis" website. It has very good coco coir buffering information and is run by a couple of college professors. They are also very much into reviewing new LED lights.
I concur, nice grow.

[bboyfromwayback]

Lack of cal mag and your ph is too high for your plants to use all the nutrients. I’ve found the sweet spot in cocoa is generally 6.0-6.1, I let my ph drift upwards to 6.2 sometimes 6.3 in late flower.

You can’t correct anything now but for your next run try providing 1tbsp of calmag per gallon of water and keep your ph lower. Some stains are heavy feeders and need even more calmag, especially in cocoa

Who do you ph your water then let it sit a week before using? Thats a new one to me. Water goes straight from the tap into my reservoir, then it gets nutes, ph’d and used immediately

[Timmeeeh]

Thanks bboy..., while I contemplate your suggestions, I would like to verify that you understand my setup. I'm not doing hydroponics, and I'm not growing in pure coco, nor coco/perlite. I'm using what Rwise refers to as a soil/soilless mix. My mix has a pre-buffered coco coir base, with compost, worm castings, perlite and a host of dry amendments.

This is (ideally) designed as a just-add-water setup, with the nutrients being provided by the the microorganisms in the substrate. As such, I am very careful prevent, or at least minimize run-off.

I'm no expert, but I've been lead to believe that the low pH levels that you're suggesting (6.0-6.1) are unique to hydro and pure coco grows. Are you genuinely suggesting such low pH for my setup?

Most of the above posts suggest I should actually raise my pH slightly to the 6.5 - 6.7 range

I let the water sit simply to eliminate any chlorine and other gasses, while assuring room temperature. Are you suggesting a reason why I shouldn't do this?

[golfnrl]

I am curious about those three fingered leaves. MJ only produces those when stressed or from genetics. You might check out this link. I'm wondering if the real answer to your problem lies in the cause of those three fingered leaves, especially if they have shown up in your other grows. That might be easier to track down.

https://www.growweedeasy.com/why-cannabis-plants-make-3-point-leaves

[Timmeeeh]

golfnrl Thanks for pointing out the 3-leaves anomaly. That completely escaped me. And it's soooo obvious. If I had to guess, it was probably the result of light stress - many weeks ago. Perhaps compounded by a magnesium deficiency. I've got the basis for some good experimenting next run. I'm looking forward to it already.

Thanks all of you for your gracious assistance!