Screwed my Sativa plant up. [HD Pictures]

Hi guys, sorry to be posting yet again. (Not learnt how to delete previous posts) and have this issue that's been creeping up on my plants for about 2 weeks. Have had them on nothing but water from my fish tank for 1 week and have tried everything I can think of to correct the issue. Please can anyone give me some guidance on how to recover these sick plants? Still quite new to growing.

When a plant becomes root bound they can't take up nutrients, Try a bigger pot with some new soil mix. Wait a few days for them to recover, then continue to fruitfulness....