well you shouldn't really be feeding them now. Most people agree to start feeding when the plant has 4 sets and the 5th is visible in the center of the growth tip.

I would back the light off or switch to CFL's they are better for seedlings.

but to answer your question. Dont be feeding them twice a day. Just give the plants pHed water and feed every few days (if you choose to feed at this point).

If you have them in good soil you really shouldn't need to feed for a week or so.