Get rid of the aluminum foil It creates hot spots and can damage or kill your plants. Replace it with something white. (I used white painted shelves... poster board would work fine). White reflects better than aluminum foil, without creating hot spots.
I cant tell what kind of light that is... if its an incandescent, it needs to be replaced with a 42w CFL (the spiral flourescents... energy savers). You should have at least 2 more lights at this stage, and youll probably end up needing more when they get bigger (assuming all of them live, which they probably all wont).