Thriving to Struggling Overnight — Need Eyes on My Setup

GrindMind · 2025-06-22T22:21:25-0600

At this point, I’m starting to see that running Autopots with Jack’s 321 might not be the most ideal combination as is. If I do continue using this setup, I’m realizing that regular top-fed flushes and closer monitoring of root zone EC might be necessary to keep things in check.

I’ve also been considering the idea of using two separate reservoirs, one with nutrients and one with plain RO water. That way, if I notice the EC climbing too high in the root zone, I could temporarily switch over to the RO water using quick-connects until things stabilize, then switch back to the nutrient feed. I’m not sure if that’s a viable solution or if it might end up creating more problems down the line. What do you think?

Delps8 · 2025-06-22T23:22:26-0600

GrindMind said:
I’m starting to think the issue may have been the light intensity all along. At first, the plants looked like they were recovering, but when I checked again a few hours later, they seemed to go right back to how they were, even though the EC was where it should be. That’s when I started considering the light as a possible factor. I realized my PPFD readings were calibrated for a 3500K light, but I’m actually using a 3000K, and I’m not sure how much of a difference that makes. After lowering the intensity and rechecking, PPFD measured around 650, so it’s possible it was pushing 800 before. I’ve since dialed the light back significantly and it’s now in the 300–400 range. I’ll keep an eye on things to see if that helps.

Here's pics from a few hours ago.

View attachment 5470256

View attachment 5470257

View attachment 5470258

Can you see a little taco'ing happening?

The difference between 3500 and 3000 at 55k lux is about 11µmol. Check out the the attached document I wrote about converting from lux to PPFD. A QB 288 V2 4000K has a factor of 0.0144 but the QB 288 V2 3000K is 0.0146. At 55k lux, the difference in PPFD would be 55000*0.0002=11

In the second photo, the leaf at the back of the plant is V shaped but that's not a typical reaction to excess light. The typical reaction is. that the edges curl inward so the leaf is semicircular, hence the appellation "canoeing" or "tacoing". Also, even thought that leaf is higher I suspect it's getting less light because it's toward the back of the grow area and light tends to fall off very significant around the periphery.

At 300-400, your plants aren't able to make much food and reducing the amount of light to a plant that's not getting excess light is like taking away lunch from your kid because he fell of his bike and hurt his arm. Light is how plants make food and rarely stresses a plant. When you reduce light levels, you're not making is easer on the plant. Instead you're taking away its ability to create the glucose that it needs to sustain (hence the word "sustenance").

The first thing that struck me looking from the photos was that the plants have interveinal chlorosis. Isn't that a magnesium issue?

Another reason why I don't think excess light is the issue is that a plant reaches maturity, in terms of being able to process light, at about week 5-6 and the light saturation point for cannabis is taken be 800 to 1kµmol. If your plants can't tolerate those light levels, the issue isn't too much light. :-)

Given that it's "hydro", it's not hygrophobic soil. VPD being out of range vs nutrient strength is a common cause of nutrient imbalance.

[checks further up thread]
Previous photos show serious nutrient imbalances. Your max temp has been 82, what about RH? Is pH in range?

GrindMind · 2025-06-23T01:08:17-0600

Delps8 said:
The difference between 3500 and 3000 at 55k lux is about 11µmol. Check out the the attached document I wrote about converting from lux to PPFD. A QB 288 V2 4000K has a factor of 0.0144 but the QB 288 V2 3000K is 0.0146. At 55k lux, the difference in PPFD would be 55000*0.0002=11

In the second photo, the leaf at the back of the plant is V shaped but that's not a typical reaction to excess light. The typical reaction is. that the edges curl inward so the leaf is semicircular, hence the appellation "canoeing" or "tacoing". Also, even thought that leaf is higher I suspect it's getting less light because it's toward the back of the grow area and light tends to fall off very significant around the periphery.

At 300-400, your plants aren't able to make much food and reducing the amount of light to a plant that's not getting excess light is like taking away lunch from your kid because he fell of his bike and hurt his arm. Light is how plants make food and rarely stresses a plant. When you reduce light levels, you're not making is easer on the plant. Instead you're taking away its ability to create the glucose that it needs to sustain (hence the word "sustenance").

The first thing that struck me looking from the photos was that the plants have interveinal chlorosis. Isn't that a magnesium issue?

Another reason why I don't think excess light is the issue is that a plant reaches maturity, in terms of being able to process light, at about week 5-6 and the light saturation point for cannabis is taken be 800 to 1kµmol. If your plants can't tolerate those light levels, the issue isn't too much light.

Given that it's "hydro", it's not hygrophobic soil. VPD being out of range vs nutrient strength is a common cause of nutrient imbalance.

[checks further up thread]
Previous photos show serious nutrient imbalances. Your max temp has been 82, what about RH? Is pH in range?

I went through the PDF you shared, and while I can’t say I fully grasp the technical details in the first part of your reply, I think I understand the general idea. It sounds like you're saying that calibrating my PPFD meter at 3000K vs. 3500K wouldn’t really make much of a difference, and that you don’t believe light intensity is the main issue here. From what I gather, you’re leaning more toward overfeeding and/or VPD being the cause.

Since my last update, I turned off both the heater and humidifier. Before that, temps were around 80–82°F and RH stayed between 60–65%. After shutting them off, things dropped—just checked and I'm at 73°F with 45% RH, and a leaf temp of 69°F, which puts VPD around 1.1–1.2 kPa.

I also let the coco dry back a bit—probably not ideal, but I had been trying different things to get things back on track, and it’s actually looking better now. The tricky part is, I’m not sure which change made the difference.

I’ll admit, I’ve been a little hands-off with the veg tent lately because I’ve been focused on a more pressing issue in the flower tent that I still haven’t fully resolved. I’m honestly not sure why I bumped the light up 10% during a flush, but I did, and the very next day I noticed problems. I’ve since lowered it by 20%, but I still don’t know if it was the lighting, nutrients, VPD swings—or a mix of everything.

It might be a little hard to see in the pics, but the issue is mostly showing up toward the tops of the plants. The lower leaves don’t seem to be affected.

Thriving to Struggling Overnight — Need Eyes on My Setup

GrindMind

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Delps8

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