I have two Polish chicks that are about 4-5 weeks old and they are starting to grow the feathers on their heads. Thte other day I noticed the one had a bald spot in the back like his/her feathers were getting pecked out. Then today I noticed the other Polish now has a bald spot in the same place. I have not seen any of the other chicks pecking at them. Is this common and what is it from? Also, what are some of the earliest male/female signs on Polish chickens?