Sorry to hear, are they in a cage? and if so is the height of the cage over 18" ? if so they are prob popping up and hitting the roof. either put them in a cage that's shorter in height or you can put mattress foam inside attached to the top, that should stop them from hurting themselves.
Good luck!
I have 6 right now, hatched them from eggs i ordered on line. Hatched out 10, one had to be put down due to a broken leg at about 5 weeks. then gave three away to a friend. now I have six laying hens. I get between 5 and 6 eggs a day. Lots of fun to raise.