Hard red spots on muscovy duck.

[Duckieduck]

I just saw these spots on my muscovy when she was having a bath. What are they? She also looks like she is a little red under her tail feathers. Ive noticed she's molting at the moment.
Brief history - she was broody, the eggs didn't hatch and she adopted the ducklings I gave her who are now 4 weeks.
Any ideas please?

 

[junebuggena]

Do you have a male?

 

[Duckieduck]

No male. Why?

 

[junebuggena]

Thought it might have been due to overbreeding.