That's 3 weeks?!?!?! Damn. This was my girl at 3 weeks. She'll be 4 weeks tomorrow, and has 5 tops poking through the screen. You seriously need more light. I also grow using CFTs, and a single 27W CFT in either 6500K (daylight) or 2700K (warm white) per plant will do wonders. Keep it about 1" above the plant.