You need to move your light a lot closer, and do you have a MH bulb? Your hps is causing them to stretch to.
MH for veg, HPS for flower. Can do a whole grow with either but it's a lot better if you do it MH/HPS.
Get an oscillating fan on them and replant them tall stretchy bitches back down in the soil and move your light closer. I can keep my cool tube 8" no problem. Even closer with my 250.