I would break up their fights when they're getting out of hand, in whatever way works for you. Sometimes, chickens kill each other. It doesn't happen often, but it does happen. It's not always new chickens that get killed, sometimes it happens in flocks that grew up together. I think it's more likely as they're nearing adulthood, with more hormones surging and asserting themselves in the pecking order, but that's just my own impression over the years.
Double check their environment for anything that could add to them being more irritable. I would make sure they are getting enough protein. Check to make sure they don't have any mites that could be biting them, which can make chickens more irritable. Make sure they have enough roosting space and aren't crowded in the coop and run, if you have one. Be sure to let them out as soon as possible in the morning and don't lock them up early, until they get past this. You don't want them locked in a tight space, frustrated to get out, while they are in a more aggressive state. Add another feeder and waterer, so they aren't having dominance fights over one source. You can use something as simple as a bowl, you don't need to spend a lot of money. When you give treats, spread them very far apart.
If you can, encourage them to do other things. I don't know what your property is like. Maybe they have enough to do already. I would do things to entice them into other activities as much as possible. Around here, adding fresh sand to their dust bathes and run always gets them excited to scratch around and dust bathe. Scratching in leaf litter is a big hit. Having extra things to hop on and climb on. Snacks, of course. Maybe dig in the garden a little and let them come over and scratch through some shovelfuls of dirt. Once they get past the worst of this, things should settle down.
Chicken fights can get out of hand, dog fights can get out of hand, people fights can get out of hand. Most of the time, they don't. Once in awhile, with certain individuals, they do. I think it's always good to keep an eye on them and be ready to tone things down. Chickens from hatcheries don't have the benefit of growing up in an orderly society, watching how to behave. They have to figure it out for themselves, but sometimes they go astray and need a little help to get back on track.
