Yellowing leaves - indoor soil no nutes

[Hyapatia]

I'm looking for advice on how to fix a yellowing leaf problem. I've seen other photos that indicate a Magnesium deficiency. But I'd love to see what you all have to say about my whole setup.

Overview of the setup

Soil: 50% Fox Farm Ocean Forest and 50% worm castings, no nutrients yet.
Light: 400W MH Agrosun bulb about 24 inches from plants
Humidity: 81%,
Temp: 79 F,
Pots: 3-gallon smart pots.
Strain: Easy Ryder plants (Low Ryder x AK 47) from Attitude
Age: About 30 days old
Light cycle: 20 hours a day
Symptoms: All three plants are starting to get yellow on almost all the leaves but only away from the veins. Yellowing began about a week ago, a few days after moving into the grow tent and also a few days after switching from distilled water to filtered tap water. Neither the temp nor humidity have changed much since moving into the tent. I've had an oscillating fan on them the whole time. But the water is probably the culprit. It seems to have a neutral pH according to several various test kits I have. Maybe there's something else in the water that messes up the plant's ability to absorb Magnesium. Since it's good quality organic soil, I doubt there is a problem with micro-nutrients not being present.

Other than switching back to distilled water, which I will do tonight, any ideas on nutrients? I'll get some photos up pronto.

 

[Hyapatia]

Sample of yellowing from a few days ago. It is much worse now.

 

[LEDman]

From the looks of it, you have a nutrient deficiency. The pic is none too great, but at least N is missing. You said you didn't give them any additional nutrients over the course of 30 days (disregarding the first two weeks, when seedlings don't require them)? Maybe that's your problem.

But I guess you're right to suspect a pH lockout issue. Most tap water is above 7 (even distilled water varies). Cannabis can only absorb nutrients if the surrounding medium's pH is below ~6.8, so that may be your problem right there. You should get some pH down and an accurate pH meter; those test kits are none too great, as I had to learn the hard way.

On your next watering, use full-strength nutes with tap water pH'd to ~6 to counteract the soil's current alcalinity.

 

[Hyapatia]

Thanks for the help LEDMan. I'll get the Fox Farm nutrient trio from the hydro store this afternoon and see if they will sell me some reverse osmosis water while I'm at it (or buy distilled form the grocery store). I'm still worried that our tap water might have other stuff in it even if I can get it pH balanced. I wasn't going to use nutes at first because I mixed in 50% worm castings and the hydro store said that nutes on top of that much worm castings would burn up the plants. But they may have thought it was for tomatoes since that is what I told them. There's an odd vibe in the hydro store since everyone knows what it is for but everyone pretends it is for vegetables. Whatever... I'm going with nutes.

Now a Nute question... The lowryders are starting to flower. One is going strong, one just starting, and the biggest one is about to I think. So I'm not sure how that matches up with FoxFarm's nutrient schedule. I'll assume it's starting to flower time. But since they haven't had any nutes so far, is there any good way to jump right in at this late date with nutrients? I've heard it is best to start with a fraction of the full dose and gradually increase it to test the plant's tolerance. But I only have about 5 more weeks to go so I would like to jump start them if possible.

I also have one beautiful Emerald Jack (Emerald OG x Jack Herer) which doesn't seem to have the same yellow leaf problem. It's had less light because it was more sensitive than the low ryders. I don't think it is auto flowering so it's going to be interesting to see what happens with it.

I'll post more pics shortly.

 

[Hyapatia]

Here's a better example of the yellowing low ryder:

Easy Ryder - 420 Magazine Photo Gallery

And here are a few of the Emerald Jack:

Emerald Jack - 420 Magazine Photo Gallery

Emerald Jack - 420 Magazine Photo Gallery

 

[Franknstrain]

they look hungry. I wouldnt worry about any diffecencies yet until they get fed. Keep an eye on your PH and you should be fine. Those girls are big enough to handle a full strength shot of nutes. But if you are still worried about it go half strength but I am sure they will do fine with a full one.

 

[YardDog35]

I agree with the advice given. From the pics it looks like you are lacking nitrogen (N), also seeing the sides of the leaves curling up some tells me it could use some magnesium as well. The Mag will be in whatever nute you feed. Since veg nutes have more N than flower nutes I would start off with a veg nute, then switch in a week or two. Start off with half strength and go from there.

Of course none of this matters if your PH is not accurate, a digital meter is a must. I like to use tap water that has been sitting for 24 hours. I found in my last grows that using filtered or distilled water added to deficiencies such as calcium and magnesium.

Good luck with everything, the plants look great!