Mallards or Rouens

[CHAVEZ94]

I have some ducklings that I just can't figure out what they are. My female mallard kept stealing all the eggs and putting them in her nest. I have had four ducklings hatch about a week ago and having a hard time determining what they might be. Can anyone help me figure out what they are? Two of them are a little bigger than the others.

 

[Aunt Angus]

I have the hardest time telling them apart, so I'm bumping this thread.

Sorry you haven't gotten any replies.