Mixing duck breeds in the same coop

Hello!

We have 3 pairs of ducks, 2 Pekinese, 2 Muscovy and 2 Mallards. They were raised together. We are having problems with the male mallard acting aggressively toward the Muscovies, especially the female. Many evenings, the Muscovies will not return to the coop from the pond. Do you have any suggestions for how we can change his behavior?
We have had them for 2 months and all are about 6-8 months old. We put the male in duck jail a couple times when we catch him being a prick.
We trained them with a duck call for feeding time in the evenings. This worked great for a few weeks we would get them all in, of course until Mr. Greenhead started acting this way.

Thank you!

Update:

We noticed the male muscovy beating up the female pekin while she was laying on her eggs. Brutal. Looks like the mallard was actually protecting the coop by chasing off the muscovee. I caught him on top of the pekin by the pond the other day as well. He has a female muscovy not sure why he is acting this way :/

Many types of fowl aren't monogamous, and males often claim several females. Another thing possibly at play is a dominance/ pecking order type issue. These behaviors, just like in humans, usually begin to rear their ugly heads, at the onset of puberty. Maybe allowing the muskovy their freedom will help. We ended up with 3 male muskovy, and no females. These boys have no interest in any sort of permanent shelter, much preferring to find their own, wherever they may be, and have not once demanded the attentions of our Rouen females, much less the chickens - thankfully.