Please help! Our 4H chicks are 3 weeks old. They have been growing great! All of a sudden today, we went out and there was one dead. I know this happens, but in looking at the others, several are missing eyes, have wounds on their heads and one is even bleading from the chest. We have 2 breeds and it doesn't seem to be affecting just one breed. What can I do to stop this or save the rest?