Its advisable to put an extra feeder and drinker in the chicken coop or run area to ensure the new hens get their share of the food. Make sure any treats such as mixed corn are spread out well in the chicken coop /run to prevent bullying or fighting. You will find the hens at the top of the pecking order get to use the highest perches in the chicken coop whilst the others will be on the lower ones of the hen house.
You will need to keep all of your hens in an enclosed run with a hen house for night for 5-10 days until the pecking order is re-established. You can rub vicks vapourub on all of the hens necks and combs to prevent too much pecking.
If blood is shed then you can apply stockholm tar or an antibacterial anti pecking spray to bare patches and wounds (clean wounds with warm salt water first), this will help healing and feather regrowth and should prevent further pecking within the chicken coop.