I don't think your going to be able to tell the sex for a while from what I remember you can't tell until your ready to bud your plant.
I know what you mean about only using ph down when I was growing I don't think i ever used ph up
if I were you I would move your lights closer I think cfls are supposed to be 3"-5" away from the plant and I would have mylar covered walls around the plant too keeps more of the light in.