Raised scales on legs?

[SquishyPandas]

Are there any other reasons for a hen to have swollen/raised scales on her legs or is it definitely scaly mites?
When I noticed it, I immediately assumed it was scaly mites, so I washed her legs and have been coating them with Vaseline, as I heard it suffocates/smothers the mites - but I haven't actually seen any mites on her so how can I be sure it's definitely mites causing it?

 

[AV8RChick]

Mites are pretty hard to see in my experience. I am a novice but I don't know of any other reason they would be raised. Hopefully, someone with more experience will chime in if they do know.