Seems like you are going through the same exact thing I am.. one of my plants is 29 inches, the other 37 in. the 29in. plant has pistils shooting out all over the place and just starting to explode since i introduced her to foxfarm nutes, a 400 watt HPS, a 5 gallon bucket and a 12/12 light shcedule. They have been flwering for a total of 6 days now, interrupted though since i had to go out of town and did not have a correct timer so they were flowering for 4 days, vegged for 3 and they have been back on a flowering schedule for 2 days now...
My point is my 37in plant has yet to develop pistils coming out from the preflower, I can bet my life on it that she is a female, but still no pistils.. I have seen many other people in our situation and the best thing to do is just put it into flowering and see whatcha got after 2 weeks, but make sure you check on them regularly jsut in case it IS MALE so you can snatch that bitch outta their before he can nut all over your girl. Hope I could shed some light, goodluck and happy growing.