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DWC & Jacks - Yellowing from light or nutrients?

  • Thread starter Thread starter Thegreywizard
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DWC & Jacks - Yellowing from light or nutrients?

Thegreywizard 13 Replies 1,770 Views
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Thegreywizard

Thegreywizard

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#1
So I've been struggling with some yellowing, and I'm not sure if it's attributed to light or nutrients

This is my second sterile Current Culture DWC run using Jacks 321

Zkittles Auto
Single Current Culture 8g DWC bucket
RO water
Jacks 321
UC Roots
Mammoth Silica
PPMs - 1700 (I do a x7 on Jacks 1 gallon measurements)
PH 5.8-6.3 (I've been running it higher lately in hopes maybe it was a calcium issue from PH under 6.0)
67* consistent temp from chiller running 24/7
AC Infinity Ionboard S24 - on 18/6 & 100% since I'm late flower and about 16" above the tops of the plant
AC Infinity 2x3 tent w/ exhaust & controller
PPFD - 600-850+ (at the highest buds, it's the most yellow, which makes me also think it's the light)

I'm using the Uni-T Light Meter with the PPFD app to get these numbers.

600-700 stays in the green, the 850+ does get into the red on the app. I still have room I can raise the light, I just dont want to lower the PPFD too much on the lower canopy.

I tried to SCROG this Auto the best I could, but it went into flower really early (even for an auto) so it is what it is. I'm going to move to photoperiod on my next run so I can fill the canopy out evenly before flipping to flower.

I also use a magnetic stirrer to mix the Jacks one at a time. Usually wait about 5 minutes to let my chiller cycle before adding the next nutrient.

The bud itself still all seems just fine, but obviously the plant is struggling.

I've been talking to Jacks support and they seem to think I'm doing everything right with the nutrients, so another reason I'm leaning towards the light.

The leaves on the lower canopy also don't seem to be suffering from this yellowing much, but still don't look perfect.

I usually do weekly water changes. Sometimes I'll go 2 weeks once in a while, but only because I am running a chiller and UC Roots to keep everything sterile.

Had this same issue with the first run of White White Auto. The flower still turned out really good, but I hope to correct this to get it to be even better.

Thoughts?


Dwc jacks yellowing from light or nutrients


Dwc jacks yellowing from light or nutrients 2

Dwc jacks yellowing from light or nutrients 3
 
#2
I use Jack's in coco, not DWC, but that's a lot hotter than I run. Your leaves are pretty dark green, and there's tip burn on almost every leaf in your pics. And I agree that's a ton of light, if you're not supplementing CO2.
 
#3
ArtfulCodger said:
I use Jack's in coco, not DWC, but that's a lot hotter than I run. Your leaves are pretty dark green, and there's tip burn on almost every leaf in your pics. And I agree that's a ton of light, if you're not supplementing CO2.
Click to expand...
Yeah I know I'm running it hot. I was thinking it was a calcium deficiency at first, so I wanted to keep the numbers up.

I'm using 6-7 gallons of RO water each water change, so x7 isn't really that heavy if I'm following their feed chart

I'll grab my parameters after each part of the 321 to see where each part puts the PPMs.

I was told a plant will uptake what it needs, when it needs it. So how can I even cut back on the nitrogen with Jacks 321 anyways since Part A is really everything altogether but the cal/mag?

I really love using dry nutrients with DWC and I have the 25 lb bags of Jacks 321 and I basically have nutrients for the next decade lol, so I'm hoping to be able to dial this in much better. I want the plants to thrive and I want to stick with DWC.

I would normally keep my PPFD in the 600-700 green range, but this dumb auto didn't fill out right. I'll get a perfectly even canopy when I do SCROG again with a photoperiod.
 
#4
Thegreywizard said:
Yeah I know I'm running it hot. I was thinking it was a calcium deficiency at first, so I wanted to keep the numbers up.

I'm using 6-7 gallons of RO water each water change, so x7 isn't really that heavy if I'm following their feed chart

I'll grab my parameters after each part of the 321 to see where each part puts the PPMs.

I was told a plant will uptake what it needs, when it needs it. So how can I even cut back on the nitrogen with Jacks 321 anyways since Part A is really everything altogether but the cal/mag?

I really love using dry nutrients with DWC and I have the 25 lb bags of Jacks 321 and I basically have nutrients for the next decade lol, so I'm hoping to be able to dial this in much better. I want the plants to thrive and I want to stick with DWC.

I would normally keep my PPFD in the 600-700 green range, but this dumb auto didn't fill out right. I'll get a perfectly even canopy when I do SCROG again with a photoperiod.
Click to expand...
Right there with you on the big bags of Jack's. The Part A is only 5% N...if you cut back on the calnit, you'll remove a lot of N. The other option of course, is to get Jack's 0-12-24. When I mix "true" 3-2-1 with RO water, I get less than 800 ppms. At 1700 ppms, you've got something else going on...from your additives or your water. I've done multiple runs with 3-2-1 flat the whole way without issues. But, maybe coco and DWC are different in that regard.
 
#5
I could be wrong, but from everything I’ve read and seen, leaves shouldn’t be dark green and rubbery. This looks like a serious nutrient issue. I haven’t used a DWC setup yet, but I did encounter something similar once when my soil became hydrophobic, preventing the plant from absorbing nutrients properly.

I put your details into Chat GPT and it replied.

t looks like there are a few potential areas in this setup that could be causing the issues with the plant’s health. Let's break it down:

1. PPM of 1700​

  • What's happening: 1700 PPM is on the higher end for hydroponic growing, especially for an auto-flowering plant like Zkittles. Auto flowers typically don’t require as high of a nutrient concentration as photoperiod plants, especially in early stages. High PPMs can cause nutrient burn and contribute to the dark green, rubbery leaves.
  • What to do: Lower the PPMs to around 1000-1300 for autos, especially during flowering. Gradually adjust and see how the plant responds.

2. PH (5.8-6.3)​

  • What's happening: The pH range of 5.8-6.3 is generally acceptable, but if the plant is showing signs of nutrient issues, slight adjustments could help. Since he's been running it higher lately in hopes of correcting a potential calcium deficiency, it's worth noting that Calcium uptake is more efficient in the 5.5-6.0 range.
  • What to do: Try running the pH a bit lower around 5.8 to optimize nutrient uptake, particularly for calcium.

3. High Light Intensity (PPFD 850+)​

  • What's happening: 850+ PPFD is quite intense for plants, especially in late flower when they are more sensitive to light stress. The yellowing at the top could indicate light burn, which often happens with excessive light intensity.
  • What to do: Lower the light intensity or raise the light further to reduce the PPFD in the upper canopy. Ensure it's not too close to avoid light bleaching and stress.

4. Water Temperature (67°F)​

  • What's happening: The water temp of 67°F is actually ideal for DWC and root health, so this doesn't appear to be an issue.
  • What to do: No need to adjust; just make sure the roots are healthy and properly oxygenated.

5. Magnetic Stirrer & Mixing Nutrients​

  • What's happening: The use of a magnetic stirrer is great for mixing the nutrients, but sometimes over-mixing can cause certain nutrients to become too concentrated if they settle. It's good practice to give the solution time to mix thoroughly.
  • What to do: Ensure the nutrients are well-mixed, but avoid over-concentrating any part of the mix. Follow the instructions for Jacks 321 carefully.

6. SCROG Method with Autos​

  • What's happening: Autos tend to flower early, and trying to SCROG an auto can sometimes restrict growth or cause stress since the plant doesn't have as much time to recover. This could potentially explain some of the plant's stunted growth and nutrient issues.
  • What to do: If you're switching to photoperiod plants next, that might allow for more control over training and canopy development.

In Summary:​

  • Reduce PPMs to around 1000-1300 for autos.
  • Lower the pH to 5.5-5.8 for better nutrient uptake, especially calcium.
  • Lower the light intensity or raise the light to avoid light burn.
  • Monitor the nutrient solution closely to avoid over-mixing or over-concentration.
  • Consider adjusting the SCROG method for autos—next time, go for photoperiods for more flexibility.
It seems like a combination of nutrient overload and light stress could be contributing to the issues with the plant. Reducing these stresses should help the plant recover.

I love AI
 
#7
Thegreywizard said:
Yeah I know I'm running it hot. I was thinking it was a calcium deficiency at first, so I wanted to keep the numbers up.

I'm using 6-7 gallons of RO water each water change, so x7 isn't really that heavy if I'm following their feed chart

I'll grab my parameters after each part of the 321 to see where each part puts the PPMs.

I was told a plant will uptake what it needs, when it needs it. So how can I even cut back on the nitrogen with Jacks 321 anyways since Part A is really everything altogether but the cal/mag?

I really love using dry nutrients with DWC and I have the 25 lb bags of Jacks 321 and I basically have nutrients for the next decade lol, so I'm hoping to be able to dial this in much better. I want the plants to thrive and I want to stick with DWC.

I would normally keep my PPFD in the 600-700 green range, but this dumb auto didn't fill out right. I'll get a perfectly even canopy when I do SCROG again with a photoperiod.
Click to expand...
easy to tell just messure your ppms today and tommorow.if it goes from 500 to 550 your are feeding too much and she will burn.i use masterblend its basicly same as jacks and max i went was 2:1 with nutes only one strain i had in my life liked 1400ppm but all of them usually like 700-900 range.now i dont know what my converson rate was or what yours is but just check your ppms from day before and you will know.

instead of calicum nitrate give it calcium sulfate most of your nitrogen should be coming from that
 
Last edited:
#8
I appreciate the feedback everyone.

That ChatGPT readout is pretty cool too.

I raised the light up another 6", so now the Uni-T is measuring everything at a max of about 700 PPFD and in the green.

I've been running my PH right around 5.8-6.0 this entire time, I only switched it up to 6.3 after looking at a PH chart and them showing calcium doesn't start getting up-taken until 6.0+ and I thought I could have been having a calcium issue.

I also didn't realize the Jacks Calcium was Cal/Nitrate - I was adding a little extra of this when I thought I was having a calcium issue

What Calcium Sulfate products do people use to pair with Jacks 321 in flower in place of their Part B Cal/Nit?

I'll do a x5 per gallon Jacks feed schedule instead of a x7 this weekend and won't go heavy handed with their Part B to help cut back on the N

I saw this PH chart the other day, and noticed Calcium was barely even touching 5.8 - so again thinking I had a calcium issue, I figured a higher PH might be better.

I know a lot of people use EC, I've always defaulted to PPMs, maybe I'll try switching over to EC to be a little more standard in hydro.


PH chart for hydroponics system 2699626311


But then I saw this chart today and it shows a much broader spectrum of the PH levels calcium is absorbed

4dda8d2e08f17d9e48eb7d9a5b079e50 3496222112


Thanks everyone!
 
#12
Thegreywizard said:
Ok that's super cheap.

This calcium sulfate gypsum doesn't mud up anything? I would think it wouldn't be good for DWC?
Click to expand...
whats there to get fucked up you have an airstone.as long as it blows nothing can go inside wash it good when you store it and your good
 
#13
I mean gypsum is basically mud/clay...

I don't know how much is needed per gallon in DWC yet, but I would think that it would gunk things up in DWC
 
#14
dont forget that you use sulfate from eposn salt(magnesium sulfat) you can overdoo on uslfur
 
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