Personally, I’d put “no peck” on the red spot, and try to not separate the boys if you don’t intend to keep them separated/ re home/ or process one of the drakes...
It doesn’t look like a bad wound, so the no peck -should- help, even with the ducks. You should be able to get it at any large feed store, or off
Amazon of you have to.
I agree that you need more hens, or to figure out another option for the extra drake. If neither of those options work for you.... unfortunately
IMO
You need to make sure the subservient drake doesn’t get hurt, but, if you aren’t willing / able to make changes, they have to figure it out. The more intervention that happens, the longer it will take.
If your “top” drake is overly aggressive w you, or the hens.... you might really consider who should go away, if that is an option.
If you have space, and want to play it as safe as possible, separate the boy that is getting beat up until you are sure the “bully” doesn’t beat up his girls, and is fertile, if that is a goal for you.
We have a lot of predator pressure where we are, so I don’t mind a (reasonably) aggressive drake to protect his ladies- as long as he’s not too rough w the hens.
You might look for a local to you Facebook page for ducks needing a home, or check CL in your area if you can/ want to increase your hen flock (or possibly to re home your extra drake).
Re homing drakes can happen, but it is not something that happens very often to be totally honest- unless he is going to go someone who wants to process him.
Not trying to be a “Debbie Downer”.... just trying to be realistic and honest. I’ve had many local to me folks push drakes on me.... they know that they will land in my smoker with rare exceptions, but. I’m honest about it, and they have a quick and painless end.
If you can’t process the extra drakes, don’t reply to those posts that have a group of hens that includes drakes.
Also. You said they have “plenty of room”
.... may i ask, how much space do they have in their coop and in their run?
Do they free range?
What is their access to feed and water?
Does feed/ water access vary day vs night?
What feed, and what types of water (poultry waterer, pool, bowls, etc)?
Also, what kind of ducks are they?