I see colours already, yum. What kind of nighttime temps do you have? As much as I want some very expensive LED's to play with I've seen the pure power of 18 k HPS back in the day (not mine), I got about 2.25 lb per 1 k HPS @ 78 days myself. The beauty of cultivation now is that you can run cabs, tents, closets, bedrooms, basements and warehouses with light and plants to fit your needs. When the laws finally make sense we'll be in the golden age of marijuana.
Loving your BBK grow, I'll have to see if they can perform outdoors in the land of the midnight sun.