Duckling wing injury or just preening?

[Countrygirl19726]

Hello to all of you,
I’m hoping I can get an answer. One of my big ducklings has developed this on her wing tip. At first I thought it was dirt but then she swam around and I was helping her clean up and noticed it was dried blood and then she had new blood after the bath. Is it due to her feathers coming in or something else?

 

[sourland]

Those are pin/blood feathers coming in, and my guess is that another duckling is nibbling on them.