Can anyone tell me what breeds I have? Any guesses on gender?

[Farm on magnolia]

Hi everyone! I got these ducklings about 5 weeks ago at tractor supply I have no idea what breed there are other than maybe the one that looks like a mallard. Looking for anyone to guide me to what breed they could be and possible guesses on gender thank you!!

 

[Bertram]

The black and white one looks like a Swedish and the brown a Buff. I agree that the one in the back looks like a Mallard. I don't know about the black one though.

 

[Miss Lydia]

solid black probably Cayuga. All are beautiful. @Farm on magnolia

 

[Jenbirdee]

i agree with both above