Young and vegitating plants prefer a light thats more on the blue side. Since the light during the spring and summer looks white it's bright, so it is adapted to the bright, white/blush light. During the fall and all the sun is more reddish and thats why you would use the HPS when it's flowering time, not this early. If you spent wads on the HPS just go get some cool white cfl's from wal-mart or continue using that. They'll still grow but I'd just try to grow in the best conditions possible.