Those plants are looking great! Wal-mart has mylar heat blankets in sporting goods, they work great and only cost about $2.50
It may be a bit early for nutes right now, but there are many ways to skin a cat.
With my CFL grow I try to utilize every bit of light they put out. Use a reflector to bounce that light from the top back to your girls. Also try to get all your plants as close to each other as possible and the position your lights over them so that they are all sharing all the lights. Hope that was clear because my mind is not.:stoned: