If I were you I would get a couple of 4ft fluoroescent lights if space permits, I have 4 and my plants are loving them. You can get them at Walmart, K-mart, or just about any hardware store and their cheap at $8-$12 a piece. If you want the biggest and fastest grows go with an hps or a mh, Although they can really get up there in price and not to mention the heat they cause. With how much light you got now they might get tall and lankey from streaching and may fall over with the weight of the plant come flowering time.

I could really help you more if you give your growing space specs.

well just my 2 cents
DP