Glad that helped. I would suggest that you feed them with some 1/4 strength grow nutes. They are pretty well stunted at this point and won't reach their full potential but should still do pretty well for you. If your new growth still looks a little pale, give them another shot or two of the ammonia.
7" net pots are actually quite big for a hydro setup. Most only use 4 or 5" ones, some only use 3". And yes, 24 watts is not near enough for growing weed. The Blackstar should work good in a setup like that.