The CFL light is probably the reason depending on the wattage. For some, shorter is better. What kind of nutes are you feeding?
If your plant is looking healthy then it is probably doing good and you have nothing to really wory about. You can only do so much with the lighting you have. Also, are you growing from seed or clone? Clones will grow shorter than seeds.
I use 6 23w CFL's for seeds and early veg and then after 2 weeks I put them under a 1K at about 4 weeks they can be up to 18 inches, but if from clone they can be about 12 to 15 inches. I just swiched to a 175 MH for early veg so I will have to see how they do.
Adieu