I introduced 3 new hens (2 golden comets and a white leghorn) to my existing flock (2 mixed breed, black java, and orbington). All about 7 months old, The 2 mixed hens won't leave the newbies alone. They stay mostly in a large coop. Even when they are outside they still chase them around. I know they need to establish a pecking order, but how long will this aggression last?