What all did you get when you bought the hps? It needs a ballast...I hope you got that much with it right? A reflector will help distribute the light downward better than without but depending on the design, they can trap & hold heat too.

Your plants are looking great...if you wait to flower for another two weeks, you will be in good shape...good strong stems to support the massive buds you'll be sprouting. :thumbsup: