can a plnt show sex before flowering

[tallslim]

i have a few Crystal strain plnts. and one seems to be showing female pistols. they just started their 18/6 hr light from 24hr light schedule. disregard these pic, their not that good.

 

[Hick]

how old are they tall'?...mj often shows preflowers, prior to actual flowering. I can't really tell by the pics, sorry