DAMN! Don't know your setup but can you move them into a larger res? I think you are right about rootbound....not knowing any details. .....give me some specs hydro.

Are you using some sort of Zyme product at present?

If you haven't already add some H202.....I would add 2mls of 35% OR--not and---OR....1/2 tablespoon (about 10ml) per gallon of the 3%. If you ARE using a zyme thing....I would stop while you are using the H202.

I hope Rhizome reads this.....he's the real hydro mind here.....

If there are several weeks left I would not use plain water....my hydro guy told me that doing that too early in flowering will cause the plant its own problems.....something to do with lack of nutrition and metabolism but I don't really understand it..... but I think that you should probably put them on 300-400ppms (a LIGHT dose of nutes at any rate).