Black spots on Pekin

[RCAKB]

Hey y'all! I'm brand new to raising ducks and recently my 2 month old Pekins got black spots on them. It is located on their head. I initially thought that it was dirt but it hasn't come off in our pond water nor the fresh, clean water in a kiddie pool. They never had spots there before. It started it 2 days ago. I want to make sure they are not getting sick. They have access to an acre sized pond (but they only stay in one area all day long) and in the evening I pen them up with fresh water and food and at night I do the same but it is located in our shop. They do not have access where they would have gotten anything on them.

 

[Poultry parent]

Sometimes mud doesn't come off when they swim. You can examine it up close

 

[chickens really]

Lots of White Ducks can have miss marks of Black on them...Normal...Adds character .....