Another Duck Breed ID Question

We have started to adjust our flock of ducks so that we have a good male to female ratio as in the past we became male heavy and they were abusing our female and unfortunately another male.

We have a pure mallard female who landed at our farm and decided to stay, a male Pekin, and two female Pekins (easy to identify). We also had a Drake that was the offspring of the Mallard female and one of the Pekin males who is a beautiful gray color.recently, we were given the 3 ducks in the attached photo by a family who couldn't take care of them and knew our ducks love our Creek and are taken care of.

I know thexactly lighter color duck is easily identified as a mallard female but she is much larger than our other wild one. The other two ducks have the undertones of the Mallard female coloring but are also black with an olive bill.

I am trying to sex these two black ducks and don't have any idea what breed the Mallard Cross is with. I do know that none of them have the curly tail feather that is indicative of a male.

Any help with the ID and type would be appreciated (or any suggestions). We are working hard so that no one gets picked on and wanted to make sure we don't have any males in this last batch.

Thanks!

I don't know why the photos didn't attach from my phone.

As a follow up to this thread, we have been spending a lot of time with the birds lately as we have some new chicks and ducklings. During our recently swapping of males and females, we traded two males (definitely male with curly tail feathers) for two female Pekins. One of the Pekins is easily identified as a female as she is much smaller than the males that we have (far right Pekin in attached photo). The other one, however, I am not so sure about. It appears to be thicker than our other ducks, and while there is no curly tail feather(s), the other males don't want it around and constantly chase it off.

What got me thinking is that our dominant male (Pekin that is behind the waterer in this photo) doesn't have a curly tail feather either. These things are getting confusing.

Any way, to recap, we are looking for help identifying the two black ducks in the first post (and more importantly sexing them) as well as finding ways to help sec this other Pekin duck. I don't have experience in inspecting the vent and am worried about inuring the birds in trying that.

Thanks in advance.