Get Help for Cannabis Plants Problems as Quickly as Possible!

[Gingerbeard]

What you have going on is common in late-stage flowering. It is not typical, just common.
Bad news is you have all sorts of nutrient lockout issues, and it is too late to do anything about what has happened to this point. Good news is you are on track for some fine dope, seriously.
You are about to get a lot of helpful advice that may help you avoid this in the future. The pictures in the link are a lot prettier but what you have going on, they have going on, and theirs is a little more genetic and a little more on purpose.
On the same website is information on what to look for when harvest time comes.
The Cannabis Autumn Color Effect (Get Colorful Leaves!) | Grow Weed Easy

[Shenandoah]

HELP!!

Problem: first time grower here. Plants are 8 weeks old, should be harvesting in a couple weeks. About at the start of flowering they started yellowing and showing brown spots. It’s worse on the lower leaves, but the tips at the top are brown and curled also. First photos are when it started, later photos are how it looks now.

Tested the runoff pH and it was too high, so corrected that over a couple of waterings. Also moved the lights further away so they are getting around 750-800 umol. But they have continued to get more crispy.

Setup: 300W AC infinity light, fox farms 70% coco, 30% perlite, dynagrow liquid nutrients

Watering: I way over watered when they were seedlings, but I’ve tried to get it back on track. Currently giving ½ gallon every 3 days and getting about 5% runoff. Could I be giving too little water now?

Nutrients: gave 1 tsp/gal of the dynagrow- Grow until 2 weeks ago when I switched to Bloom

Temp/humidity: Temp 70-80 deg, humidity a little low at 30-40%

Any suggestions would be helpful!

[Bluey]

Here's an older article on root zone health explaining how we thought it all worked back in 2016.

https://www.cannagardening.com/articles/root-zone-temperature-and-plant-health

Dissolved 0² or DO does leave the surface water over a period of time but it can take a little while to reach equilibrium, eg. overnight, without help, eg. Stratification. It is leaving the water in the root zone though so can it still be used by the plant or soil microbes? Is it raising the 0² in the medium which in turn keeps it dissolved longer in the H²O?

CO² at the roots which is also beneficial to a healthy crop is 200 times more soluble than O² in water. That is my understanding although the above article states CO² serves no purpose for cannabis in the root zone..I'm not so sure about that.

[Bluey]

Here's an older article on root zone health explaining how we thought it all worked back in 2016.

https://www.cannagardening.com/articles/root-zone-temperature-and-plant-health

Dissolved 0² or DO does leave the surface water over a period of time but it can take a little while to reach equilibrium, eg. overnight, without help, eg. Stratification. It is leaving the water in the root zone though so can it still be used by the plant or soil microbes?

CO² at the roots which is also beneficial to a healthy crop is 200 times more soluble than O² in water. That is my understanding although the above article states CO² serves no purpose for cannabis in the root zone..I'm not so sure about that.

[Rootsruler]

Bluey This was a debate that I would see when I was working at licensed grow ops. Most of the botanist said that cooler water does hold more O² but that it dissipates quickly trying to equalize with the atmosphere. They felt that warmer root temperatures allowed a lower viscosity of the sap in the roots helping the plant move nutrients easier. Feed temps were usually around 72².

[Bluey]

Rootsruler keep water temp down around 20⁰C or lower for maximum O². But remember all compounds in air are beneficial for healthy roots especially CO² and I'm guessing N also if growing in soil.

[Eclipce]

I have improved the watering and am still working on it. Previously, I was watering too quickly, and the water would just run out of the pot. The plants are starting to feel better now.

[Rootsruler]

I'm going to start playing with fertigation as a way to maximize the O² exchanges.

[Smallgrow]

After 5 years of growing I’m still working on watering. Some will think that’s nuts but I think so many issues come back to watering for a lot of grows. People chase all sorts of things needlessly.
I grow in living soil with good nutrition, light, and environment so watering is really the other piece of the puzzle
Keep working on it

[Eclipce]

Thank you, everyone. It seems the issue is with my watering.

[Rootsruler]

You really want to wet ALL the media not just on top of the root ball.

When you water the entire media the media in the rhizosphere, the area adjacent to the roots, will dry first as that is the easiest for the roots to access. Once it gets dry the plant will signal the roots to go looking for more water. Having moist media beyond the root ball will get your roots to grow larger and longer.

I don't elevate my pots. I leave them in plastic bins and let the runoff resoak back into the cloth pots.

[Bluey]

No rinoff in a soil grow without nutes. You wash out the goodies.

I don't know. I don't use fabric pots.

[Eclipce]

I’m not getting much runoff because my pots are on the floor. In the next few days, I’ll lift them and start watering to achieve about 10% runoff. Could the problem be that I’ve only been watering around the center near the seedling?

[Bluey]

Are you getting much run off? Try for almost zero run off.

I'd spread out the watering a bit and see if you can give it a bit more. I'm not actually sure what is causing the deficiency I doubt it's a lack of any calmag, I think the problem lies elsewhere. Lift the pots off the floor. Be conservative with light.

[Eclipce]

I’m growing in soil. I’ll keep an eye on the top leaves. If the situation doesn't improve, should I give сalmag?