Organic stuff doesn't always work as well in hydro because you need bacteria to break down the nutrient to a compound that is useable by the plant as far as I understand it, and you don't always have enough organisms to break down your nutrient. I don't know how you're feeding them but, as I assume you're using the GH 3 part, use the lucas formula and it should help clear up two of the possible issues. Stop using the grow (the green shit) altogether. For your veg plants use about 5ml of the micro and 10ml of the bloom per gallon. For the youngest veg plants and newly rooted clones I use even less than half than that. For flower use 8ml and 16ml of each per gallon. If you are not already doing this you may have an excess of nitrogen and an absence of sufficient calcium/magnesium. If you're already doing that I'm sorry for the rant and I would just get your self a liter of cal mag from botanicare, technaflora or GH. I use MagiCal from technaflora cuz it like $10 a liter or somethin. Between adding a few ml of this per gallon and the lucas formula all my mag issues are solved. Whiteflour has a point too. I would get yourself a bottle of chemical cal-mag ferts and see if you can't fix your problems. If that doesn't work buy some florakleen or clearex and flush your system for a while as it may be lockout due to build-up or ph fluctuations due to build up. It certainly wouldn't hurt to get yourself a cheap little ph tester kit at least. Good luck.