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?
Help_Needed Reviewed by Help_Needed on . 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/hydroponics/151678-sog-gone-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 - Rating: 5