you will have to leave them a bit longer,what i done was take cutting of all my plants and put them under 12/12,remember to mark what plant each cutting came from,once i determend the sex i threw out the cuttings and the mails took new cuttings of my female plants and when my first harvest eas done i had all female going strait in again and before i put them under 12/12 i took more cuttings and so on ,but once your cuttins have shown their sex, better binning them as no use reveging them.
hope this helps as im new at this myself,peace