Then it is possible that your lights are to close for the moment. What is your Light Config... ie, 23W CFL, 68W CFL.... i use 23W 5000k/6500k CFL's for veg and i use 68W 2700k CFL's for Flower. But they still produce enough heat that they can heat stress your babies. as for one growing faster than the other i wouldn't be to concerned if they are just at different distances to the lights, due to one being heat stressed more than the next. However, i have heard rumor, so don't quote me on this, that males grow faster than females. i haven't ever experienced it so i would not truly know. But i think your fine to be honest. just monitor your temps and listen to the veterans above that have the most knowledge about nutes and watering. you'll be fine.