My advice is to keep as few roosters as you can and still meet your goals, whatever they may be. It’s not that you are guaranteed problems with more roosters, just that the more roosters you have the more likely you are to have problems.
I don’t have any chickens with those strange things on their heads so I can’t speak from experience on that. I don’t know if the damage is from the roosters fighting, from the hens pecking at those headdresses, or what I more suspect, one was injured a bit in the fighting and the hens are now pecking at the blood and open wound. Chickens will do that. If one has an open wound they can (nor necessarily will each and every time but very often do) they can become cannibalistic and kill that wounded chicken. For his safety I’d remove him from the flock until he heals.
I’m not a believer in magic numbers. That 10 to 1 ratio Cynthia mentioned is based on fertility in a certain situation. That’s the ratio hatcheries have discovered provides best fertility in a pen breeding situation. That’s where you might have 20 roosters in a pen with 200 hens. It’s not going to stop roosters fighting and it’s not going to stop over-mating in a pen breeding situation or any other. It’s not a bad ratio. 10 to 1 certainly makes for a nice flock. But the age of the chickens, personality of the individuals, and how much room they have has a whole lot more to do with peace in the flock that hen to rooster ratio. One rooster by himself can easily keep more than 20 hens fertile if he is reasonably active. That 10 to 1 is for a specific purpose (fertility) in a specific management technique (pen breeding). If you keep them for different reasons or in different circumstances that ratio doesn’t mean a lot, though I still recommend keeping as few roosters as you can and still meet your goals. There is nothing wrong with a high hen to rooster ratio.
What you are seeing is a flock of chickens go through adolescence with no adult supervision. If you have an adult mature roster and some mature hens the process is usually less stressful but with a bunch of adolescents it’s still not going to be calm.
The males normally mature a little earlier than the pullets. Hormones are running wild and they have no self-control. It’s not only about sex either, it’s about flock dominance. Between them your two cockerels will decide which one is dominant. Usually that involves some skirmishing and a lot of chasing and running away. It’s possible they will fight to the death but usually they reach an accommodation and work together to defend and manage the flock. Another possible outcome is what I think you are seeing. One gets injured and the rest of the flock cannibalizes the injured one, even if he is the winner.
The pullets usually mature a little later. They don’t know what is going on when the cockerels make a move toward them so they often resist. The mating ritual is not just about sex, it’s also a dominance thing. The one on bottom is accepting the dominance of the one on top, either willingly or by force. Those pullets aren’t ready to be dominated so they resist or run away. The cockerels chase them and try to force them. It’s not always pretty, but if you can get through that phase they normally all mature, gain some self-control, and accept their roles in the flock. You usually don’t see these types of problems very much with mature chickens but with adolescents it gets real chaotic.
You may have another element that may make it even more chaotic than normal, other than the pecking on the injured cockerel. Normally the cockerels are bigger and stronger than the pullets at this age. But I suspect your Polish cockerels are bantam and the pullets are full-sized breeds. Those cockerels can’t necessarily establish dominance by brute force.
What can you do, other than separating the injured one until he heals? You could live with the situation. Eventually they will settle down but I can’t tell you if that is a few weeks or many months. A lot of this involves chasing and running away. The more room you can give them to actually get away the better, but that does not totally stop the hormones or give them self-control.
You could get rid of both cockerels. The only reason you need a rooster is for fertility. Everything else is just personal preference.
You could get rid of one of those cockerels. That will stop the fighting but it won’t stop him trying to establish his dominance. You’ll still see some turbulence until the flock matures enough for him to establish his dominance, but it may not be as bad.
You can put the two in a bachelor pad. Keep them separated from the pullets. I’ve done this before. There is usually very little fighting if there are no females to fight over and the pullets certainly won’t be bothered, though you may see the pullets sort of hanging around close wanting the company. This could be a permanent arrangement or when they are about a year old, turn them loose with the hens and see what happens. There would probably be some skirmishing but they should be mature enough to work things out between each other and the hens.
I know. Long winded and rambling. Hopefully you can get something out of this that helps. Good luck!