sexing before flowering

Some of my plants have started to show signs of sex before i turned lightning on 12/12. Any suggestion as to how this could happen?
i use a 105 watt flowering cfl and have done all along..

what should i do now?
should i turn them to 12/12?


for the record:
they are not very tall: 18 centimeters from top soil to top.

when a plant reaches full maturity they will show there sex

how long have you had them in veg for

Mine did the same. I went ahead and flowered them, but from what I know, you dont have to. Mine werent very big either, like 8-10 inches. Do you have pics? We like pics.