I have some baby chickens (about 10 weeks old) there are 4 with one mother. I am not sure about sex yet. I have seen some normal pecking but yesterday one of the chickens start chasing and pecking it's sibling. It pecking it so hard it was cut and bleeding right under the eye ball. I took the injured one inside, cleaned it's wound and kept it here over night to let it heal. The other chicken was relentless and keep chasing this poor baby so it was hiding. The mother saw it but didn't seem to care. what should I do? They free range and have a whole barn, food and water so space etc... not an issue. There has been no change since they were hatched, no new stress. Why is this baby being mean?