so i recently received three Millie Flur d'uccles from a family friend according to her they are "triplets" and have been together their whole life. One of them is acting very aggressive towards the other two, pecking at them, pulling feathers out(no blood but i'm worried about it getting to that point). is this something that is common and to be expected when you remove a couple birds from the larger flock and but them in a new pen? do they have to establish a new pecking order or does this seem like it could be a bigger thing