You always get this problem when introducing newbies I'm afraid, especially if they're docile. It's largely a question of space - if their run doesn't provide a minimum of 2 sq metres of floor space over bird, the established flock will be extra resentful about the 'immigrants' and the new girls don't have room to get away from the inevitable bullying. It's a good idea to separate them with some sort if netting barrier for a couple of weeks, giving the new ones a temporary box to sleep in, so they can see each other and get used to it, without any pecking going on. If you can let them out into a garden, they will be happier as well, and can eye each other up from a distance. Ideally, new birds should be quarantined separately for at least two weeks, to let them settle down after the stress of moving home, and mainly so you can see if any illnesses or infestations emerge which might affect your flock.
When you think they are ready to be re-integrated, you should take the new ones out of their box after dark, when the old ones are settled and asleep, and put them on the perches in the main coop. Then they will all sleep together, acquire the same smell, and emerge together next morning. This won't entirely solve the chasing and pecking but will help. If you have one very aggressive hen, I would separate her at this point, into the enclosure the new ones have been using, whilst the new ones settle down with the others. Re-introduce her when they've settled, after a few days, and with luck she will have been taken down a place or two in the new flock pecking order, and may have to knuckle under a bit herself.
Watch out for actual bloodshed, though, and have some purple antiseptic spray ready if this happens, which will camouflage the blood and assist healing. If bleeding is bad you must separate the affected bird or the others will all be attracted to it and will peck it and make it much worse.
