Could this be molting or does it look like injury, pest, or disease?

[sophiehatter1057]

4 weeks old, two of eleven chicks affected (including a very dominant one, and a very shy one)

 

[casportpony]

Have you checked them for lice and mites?

 

[sophiehatter1057]

Have you checked them for lice and mites?

Yes, and I'm not seeing them, but my eyesight isn't amazing. Does this look like what we are dealing with? (They've only ever been indoors)