your plants dont really look ready to flower imo, how old are they? Depends on what you want to achieve tho. if your looking to maximise your yeild id be thinking longer veg and more light, 400w hps?
Your plants look like they are suffering some sort of deficiency (pale yellow leaves and red stems) and they also have a little nute burn so that would suggest you have over nuted and not flushed so you may have altered the PH of the soil leaving the plant unable to take up food.
I also notice you have curled leaves, i had this problem when i didnt let my pots dry out, my plants never had the chance to take up o2 and just sat in a soup of soil, nutes & salts, once i realized what i was doing i flushed em out, then let them dry before i watered again.
Dont think i being critical by pointing these problems out, you seemed to have made a decent start to growing but you have quite alot you could improve on in a very short ammount of time, say 2-3 weeks you could have the plant in much better shape when you do flower.
If you put that plant to flower now it will just eat up all the nutes in the foliage and all you hard work will go to waste.