on my current grow I waited till my 4 fems were 2 foot tall to switch them to bloom, and in the beginning stages of bloom they still grow, so you might want to think about height control. I would recommend blooming them early, probably around 1 to 1 1/2 ft. I have a 6 foot setup and mine are 4ft now and looks like they're finally tapering off. i'm only using 4 T5's with a T5 reflective fixture and mine are bushy and flush green.

My first grow I was unlucky, my 2nd grow I was even more unlucky, and finally when I planted 8 seeds, I got 2 fems and cloned them after that. Best of luck with your grow, your gonna love it!