think of it like this, they wont show gender til they hit puberty. and you got infants there.
i have some in vegetative (18/6 light/dark schedule) that are way past puberty, and they are some horny ass ladies, with the first set of pistils (hairs) jutting out around an inch at the top few nodes. they want the sex. they want pollen and they want it bad. dirty whores!
either way, dont rush it. they longer you wait, the more sure you are that your not chopping down a female (thinking its male), the more sure you are that she is ready to flower, and eventually, the more sure you are that they are ready to be harvested. =)