would probably go ahead and flower them and they should show sex usually within a couple of weeks while it is possible to sex the plants in veg stage and generally they will show when they are 4-7 weeks old but in your case your plants are stretched and look way under developed for their age probably due to bad lighting for the first 3-4 weeks of their life so wouldn't expect to much from them, flouros are ok for starting seedlings under for a few weeks if kept close but when its time to flower you would be better off with a hps light which im sure you will find out, while some use flouros and really cram alot of lights to attempt to adequetly light the sides and the top of the plant for flowering a hid will always out perform them.