They say 12/12 should be switched to, only after this stage, for best plant development. Too early and you run the risk of 1) Stress-related sex problems(hermaphrodites), 2) Abnormal bud growth. Now I don't know if they are right or wrong about that, but I have the time. So far it has proved true here, I'll get to that in a moment.The Cannabis Grow Bible said:Initial calyx development is not photoperiod responsive. You do not need to change your light photoperiod in order to find calyx development. Calyx development is a natural part of the plants life cycle and occurs when the plant is mature enough to display sex.