Welcome to BYC. They could be pecking each other if you are not seeing any tiny bug or eggs on their skin and feathers. Make sure they have plenty of room in their coop and run, are getting enough protein in their diet in a balanced layer feed, and that they can get outside to roam daily so they won't be bored. Limit lighting to 12-14 hours a day. If you see lice or mites, permethrin or other treatment may need to be applied every 7 days, while changing bedding in the coop. There are anti-pecking creams available, and products such as Nustock cream, BluKote, and menthol ointment can be used on bare spots to discourage pecking.
Edited by Eggcessive - 5/28/16 at 5:12pm