I have a flock of 45 chickens all together. 6 Roos 39 hens. Some are pullets. My Roos always gang up on my hens every time they "mount" and they all take turns and I've lost 4 birds because of this. This morning I lost my ameraucana pullet because of it. And I've lost 3 hens already laying because of it. Can anyone tell me why they're doing this? And how I can stop them?