A week ago I integrated 2 pullets in with my 2 slightly older pullets (only a couple weeks older) after full quarantine, and a couple weeks of getting to know each other through a wire gate then free-ranging. The 2 new girls haven't been allowed up to roost with the 2 established girls so yesterday I opened up the nest boxes and re-arranged the coop, hoping that the new additions would mix it up enough to allow the new girls up to roost. It worked with a minimum of pecking last night. Today My established EE has started pecking everyone's vents. She also pulled a feather out of the newbies side and ate it. This is a new behavior as of today. They are not cramped or bored, and they have multiple feeding and watering stations for easy access to food and water. The roost is 4 feet long, giving each bird a full foot of room and even while free ranging today, the EE ran across the yard to hunt down and peck another girl's vent on multiple occasions. She even pecked the head Pullet's vent which earned her a sqwauk and a sharp head peck from the dominant pullet. The 2 established girls are 21 weeks old, new girls are 18 weeks. No one is laying yet and everyone is on grower feed with daily greens and grit, plus apx 5% treats of mealworms/grubs and whatever they forage out of the yard & garden. There is no supplemental light. What do I do? Do I remove the offender for a few days to shake up the pecking order and knock her out of her spot? How do I fix this so I have a cohesive flock?