IMO I would wait to flower. It really is amazing the difference you can make just waiting a couple extra weeks. A lot of the time a plant will show you when its ready to flower. You will usually get pre-flowers (depending on light cycle) that will shoot little pistils out if its female, or a sack at the end of a stem to show male. I always wait for pre-flower befor I go 12/12 because this assures they are mature enough to produce quallity buds. You usually dont have to worry about this as much with clones since you already know they are female but a clone should still get a solid 2 weeks of veg before flower IMO, gives it time to make a new home and get settled in.