You're gonna have three tiny plants in 2 sq. ft. I guess/hope you're doing a SOG or something.

What size fluoro tube are you using? The smaller (in diameter) the tube, the better. Thinner tubes are a lot more efficient. The number on the tube should tell you the size--T12s are the biggest, T8s are thinner, T5s are the thinnest (and best). 4100k is fine for veg growth. I'm curious to hear what others think, but IMO and experience, plants don't start needing huge light until about two weeks into growth. It's pretty easy to tell if you don't have enough light. Around week 3, plants really grow fast (depending on your strain, of course). I'd say you'll be okay for the first two weeks with the tubes.