Dark leaves - possible N toxicity?

Ok, I've got kind of an oddball situation. I've got 6 clones in a DWC system sharing a common reservoir - you can see a pic here : http://boards.cannabis.com/hydroponi...overboard.html. They've been growing fast and I've been gradually increasing the nutrient concentration, intending to push it as high as I can until I just start to see some nute burn, and then backing off. This morning I woke up to find that one of the six appears to be showing signs of nitrogen toxicity - dark leaves with a bluish cast. The stems around the leaves are starting to turn purple too.

Other info -

Lighting - 400w HPS
Nutrients - Lucas Formula 1250ppm @ 0.7 - this is still a touch too low and I was planing on bumping to 1350ppm this morning, until I saw the problem.
Ambient temps - 82F, lights on; 72F lights off
Reservoir temps - 74F
pH - 5.7

The odd thing is this is affecting only one plant. Since they're sharing a reservoir, they're all eating the same food. And they're all clones from the same mother, so they're genetically identical. Also, the Lucas Formula is actually somewhat low in Nitrogen. Is it possible that some other nute is being locked out, causing the plant to take up too much N?

This one's got me stumped. Any ideas?

Are you using a zyme product or some H202 to prevent disease? Those are all fairly crowded, leading to some great conditions for the roots to develop problems.

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Originally Posted by Weedhound

Are you using a zyme product or some H202 to prevent disease?

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I put a liberal dose of Hydroguard in there a week ago, Monday. It's been 10 days so they could use another dose today. I haven't checked the roots in a few days, so that might be a problem.

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Those are all fairly crowded, leading to some great conditions for the roots to develop problems.

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Yeah, the crowding is a bit of a concern, which lead to my other post. I think I let them get too big before switching to 12/12. And I'm considering pulling 2-3 plants and focusing on quality vs. qty. Even if I only get 2oz per plant - which is very doable based on my last grow - I'll end up with way more than I'll need.

Mostly I think I wanted to run this as a SoG, just for giggles, but the more I think about it, this system probably won't support a true SoG very well. Hmmmm....

Ummm.....how far into 12/12 are they? I think you may well need a bigger container. Careful pulling some and make sure the roots aren't all tangled together so you don't rip out the roots of ones you want to keep.

And yes, I'd keep you hydroguard up to date and add it as often as you can.

good luck.

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Originally Posted by Weedhound

Ummm.....how far into 12/12 are they?

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The started 12/12 on Monday, so four days now.

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I think you may well need a bigger container.

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Yeah, I've done three plants in here without any problem, but I don't think I'm going to be able to do 6.

Eh, I chimed in on your log thread. I also think that 6 is a stretch (har har har) for that size system. Maybe you could toss some Bok Choi in there while the pot is putting on weight- lol!
:D

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Originally Posted by stinkyattic

Eh, I chimed in on your log thread. I also think that 6 is a stretch

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LOL. Last time I grew this strain, they stretched vertically...a lot. But that was under CFL's. Now that I've got the HPS in there this time, all of the initial growth has been horizontal...which isn't necessarily a bad thing. But I wasn't really prepared for it either lol.

Yes I came up against exactly the same issue when I went to a longer veg period and a 400wmh instead of my cfls. The damn things GROW!!

Well, I went ahead and removed the sick plant and the two smallest plants leaving just three plants in the grow. The roots and all of the plants look very healthy. The only interesting thing of note is that the roots of the sick plant had a very different growth pattern from all the other plants. All of the healthy plants have roots that are about 15" long - reaching deep into the reservoir - but relatively narrow. The sick plant's root mass was only about six inches long, but about 8 inches wide. Not sure if that means anything, but it was interesting.

I also moved the remaining three plants around to give them more room.

Thanks for all the help.

Much better....but I still think you're going to have a bit of a fight later on....they look pretty damn happy and growing well there.