Need help sexing ducks

[BReeder!]

We have 3 rouen ducks from Farm & Fleet. They are about 2 months old I think. I just put them in the pond today. They were in a brooder until now. I think I have 1 female and two males. I was hoping for 1 make and 2 females... what are your thoughts on the sex of these ducks? Sorry if pics are not the best. They are moving around a lot and playing in the water.

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[Loopeend]

Do they quack?

 

[Loopeend]

For the rest; 1 female; 2 and 3 male. But you are more sure when they are not in their nuptioal feathers (or what it is called; certain colours; before getting their adult feathers; ALL first look like females. But the green head-sheen... how they quack (or not) can give more certaintly.

 

[chickens really]

Looks like one Hen and two Drakes.