It may be "suvival of the fittest". Not all chickens play the one who decides who shall recover from sickness or injury, but most DO. Sick birds need to be separated for a chance at their recovery. Starts with baby chicks, who sometimes "do not like" one of their mates and even kill it! It is up to us to protect them, feed them well, and keep them safe from predators. Love them all! Good luck