I am new to this!! Please help!!

[Blacksmithchic]

Did a quick Google search, the only thing I found for baldness at the back of the head and baldness at the rump is from excessive mating. Your ducks seem a bit young for that, but you never know...I would supervise their behavior closely over the next week or so and see if the drake is mounting the duck.

You usually want to keep three females or more per drake, otherwise the drake will exhaust them and possibly kill them from mating too much.

 

[Blacksmithchic]

It could also be from them scratching themselves. If you're sure there aren't any mites (which are small, you have to look very close), then check if they're getting their feathers in. If they are, they may just be scratching at their down while the new feathers come in.

 

[Amiga]

Please tell us again what she eats, how warm the brooder is, what the bedding is, where she goes, what she comes into contact with.