Yes I would flower now , they are getting real tall . How tall is your grow space ? Plus dude remember you got another 8 -12 weeks when you start flowering so the earlier you flower the faster you get your smokey smoke. Also , I know they always say they double in height, but that is simply not the case in my experience . If they are 3ft now, they will probably get to 4.5 ft tall at finish. They look really healthy btw ... good job !