Many problems to this grow.
1) Who said you can go 12/12 from seed to finish? WHO???? You have been sadly misinformed, and it shows by how sad your plant looks after 4 weeks. Erysichthon was right. The only strains that handle a constant lighting cycle (same cycle) from start to finish are autoflowering strains, and even those require 18/6, 20/4, or 24/0 depending on who you talk to. 12/12 is definitely not enough, unless you want to spend a year to get meager amounts of bud.
2) You need to do some more reading before you disappoint yourself. Vegetative phase is required for plants to grow their stems, leaves, and roots. People start flowering once these are established.
3) I can tell you right off, that if you continue with what you are doing right now, you will be lucky to get one good joint out of that. Good thing you aren't growing an autoflowering strain (or are you?) or else you'd probably be screwed already. You will want to change your lighting cycle back to 18/6, with 6000K CFLs for veg, and you need to really get a bigger pot. Also, MORE LIGHTING. You don't have enough lights, and that's probably the main reason your grow is so slow.
4) I am appalled no one is telling you you're messing up. Oh well.