Personally I wouldn't veg for so long - those are some big plants! Light penetration is going to be a bitch.

How old are your bulbs & are they MH or HPS?
Sidelighting?
Whats your high/low RH%?

Personally like my room to get a little warmer than 78, usually about about 84. I try to keep my humidity around 50-60% but have gone as high as 70%. Some of the sativas really love the humidity, but with the strains you're running I would stick between 50-60%