A yellow scab on one of my hens— mites or infection?

[Tyranno-Chicken Rex]

Today I noticed a yellow scab on the belly of one of my hens and the area is pretty bald there too (although feathers are growing in). There are also bald spots under both wings, which makes me think it might be mites because I heard they like to stay under the wings? I didn’t see any directly however. I was also concerned it might be some kind of infection or illness. She seems healthy and none of the other hens are showing any scabs or other signs of infection or mites I think. The scab is at the bottom of the picture but please tell me if you need a better one.

 

[Eggcessive]

Is the scab on her breast bone (keel?) That is a common area for a breast blister which is usually from lying on damp ground or bedding or on a rough roost. It happens usually when a hen is not active, and spending more time on the ground or on the roost because they are sore. You can clean it with Betadine or generic Equate First Aid Disinfectant from Walmart. Make sure if she is sitting around a lot more than usual, that bedding is clean and dry. If roosts are round they can be sanded ir padded. Here is a good link about breast blisters:
https://poultrydvm.com/condition/breast-blister