I have some 13 week old hens and some 10 week old hens that have been together for 4-5 weeks now with little problems. Today, one of the 10 week olds that is towards the bottom of pecking order was fine when I left the house at 3p.m. Returned home at 6 p.m. went out to check feed and waterers. Saw that this bird was bleeding bad on back. Had a strip about 2 inches wide by 4-5 inches long that had no feathers and was bloody. I know birds, like humans are stressed by this heat and humidity we have had last 4-5 days. BUT How does a bird look fine and then 3 hours later be bloodied and weak? She was not a specific target before. Had no pecking issues or feather loss. I isolated her and applied some antiseptic. Would heat cause a flock to do this? They have 2 waterers that I check 3 times per day. Feed and a roofed run on part that provides shade. Help!!!