As you are growing with CFL's and not doing LST or SCROG, it would be best if you put them into flower before they get too large. At 28 days veg my plants are around 14-16" high and they are about 26" high once they have stretched during the 1st 2 weeks of flower. Even at this height my 2x125w CFL's struggle to penetrate the lower leaves and I am only growing 2 plants.

If they were mine, I would wait till they get 12" tall and then go into flower or I would just flower them now and see how I got on. The longer you veg the more bud you will get, as long as you can give the plants enough light and food to make it.

If you plan to keep using CFL's have a read up on LST and SCROG for your next grow, it should give you a better harvest than just letting them grow naturally.

(the only reason I am letting mine grow naturally is because I want to test how much these techniques increases harvest size by)