Flowering when to start

Ok, the seedlings are getting bigger now they are 7 to 8 inches tall. Is it time to start flower stage? we dont have much room so have been told to start flower and they will still grow another foot or so.
How do we send them into flower mode? Someone told me about this molassis for making bigger buds??? is this a food? I was planing on using fox farm bloom is that good food?
I posted some pics so you can see my set up

looks good now..switch the lights to 12/12 and start giving them the bloom nutes. if you use molasses get blackstrap unsulphured molasses but i'm not sure if you can use it with your feeding system so wait for some one who uses the same set up you do to tell you if its ok.