Generally, you should refrain from using aluminum as a reflective for the light source, as it actually doesn't do much. Instead, you should take that off and either paint the walls white or put in some reflective mylar along the walls.

Second, to determine the sex, you must take a magnifying glass and take a picture of the top of the plant, and pictures where the stems meet the stalks, and post it up here. That plant actually looks young. What lights are you using, and how old is it? What are you feeding it with? How long does it get light each day? Do you know what strain it is?