They are getting "leggy" reaching for the light. I would put a small fan to blow on them to strengthen them up. When I was starting seeds in a cold climate for spring transplanting I would leave the lights on 24/7. I would use normal fluorescent fixtures just an inch or so above the seedlings and raise as they grew.
I used to be shocked when I would go to Alaska in the summer and see the vegetables they could produce in what is basically a 2 month growing season due to the extended time the sun is out.
Shawn