just to throw this out there my plants are at 40 days at this pic and I am a noob, ( I am not looking to make others look bad, just HPS to look good)
not to take away from othres with CFL but HPS is bomber for flowering. next grow I am going to CFL for Veg and HPS for flower.
riging up some sort of vent from the outside, even drawing cold air through a window will make a big difference esp if you are in a colder climate.