I need some advice, I raised 5 babies till they were 2 months old, I put them in a smaller cage inside the big coop for 2 weeks to get the 2 hens and rooster used to them. I finally let them out in the big coop when they were almost as big as the others and they seemed fine all day, the next morning my babies were dead, the others killed them. How do I introduce new chickens on the existing coop?