It's hard to see if they have drake feathers from the pictures but the easiest way you could tell yourself is by their quacks. The boys are very monotone and the girls are loud and annoying. Males will also have a white ring around their neck and a yellow/greenish bill. I'd say they look like girls.
Here are some more pics. The khaki Campbell's like to photo bomb... I have the light the brown one that I think is female and the other two darker ones that I think are male... They have a green sheen on their heads. My husbands says the other way around. Do these pics help?