When you say scratching her backside, do you mean her butt or something else?
Mostly white pit bulls are not standard to the breed so they end up with a lot of health issues including skin allergies, like you are seeing now with her being deaf and the recent skin issues.
It would be a good idea to bring her to a vet, but until you can start bathing her in a gentle medicated shampoo like Malaseb. Not the tea tree stuff you have been using. It’s possible those types of shampoos could aggravate it more.
I’m also not familiar with the food you are using. Can you show a link to it?
