We bought 8 hens and a rooster when they were about 2months old. Everything was fine until they got older. Then out of nowhere the hens started to mount one another and pluck the feathers from the backs of the little hens. Now, tonight, they killed one of the hens. Her neck was snapped and after burrying her, some if the hens began to attack another hen. How can I prevent them from killing another one? I'm upset and anger that they did this when they never have before. Please help.