Yup, they’re cannibals too under the right circumstances.
When we first got chickens (I now have a couple of dozen and the same in ducks) we worried they’d be scared of our dogs…. Nah the dogs are scared of the chickens!
I’d recommend keeping them separate if it’s causing problems, sounds like you have two runs and coops? You sometimes find you have one hen who is aggressive and causes issues, I’d try and identify that one and isolate her.
Any new birds will need to find their place in the ‘pecking order’ and there will be scuffles while that’s identified but I’ve never had any bird actually injured or killed (in a great many years of breeding and keeping poultry). I strongly feel you need to find the aggressor and isolate or rehome that bird.
One final thing, they do have enough space, right? I have about 1/3 of an acre per two dozen birds and they rotate through a full acre (so a week in each area with one area empty). This is enough for them to free range nicely, eat bugs and insects and get away from each other if needs be. Coop wise, each run has a 10 x 8” shed with roosting bars, egg boxes etc. chickens need A LOT more space than small commercial coops and runs provide and aggression will be worse if they’re crammed together.
Hope it goes well, chickens are honestly fantastic pets when you get to grips with them