I have 15 guinea, tonight as we were trying to get them into their coop, one flew down off the roof into the group. The group immediately attacked him. At first I thought one had a worm or mouse and they were fighting over it. There was nothing there. They simply beat this other guinea nearly to death. Even when I tried to break it up and get the beaten one out a couple attacked it. Is this normal? Why would they attack one of their own? They have lived together as a flock for 2 months now. I had 5 and added 10, I have no idea which is which. They are all about 5-6 months old. They are normally so comical and fun to watch, this was neither.