Muscovy duck not laying - any tips?

[Onlyducks]

This is a picture of my one male and five females. The male is much larger than the females, though it doesn't show so much in the picture. The females have varying amounts of red on their faces—I really thought one was male, but the seller swore it was female. She is about 2/3 the size of the male, so I'm guessing he knew what he was talking about. She and the other four females are the same size.