Skin Problems Bald Spot

So I discovered this bald spot yesterday and called the vet yesterday and she prescribed Matisse Revolution. But here's the weird thing about this... He doesn't scratch anymore than what I consider normal, I'm in no way concerned about his amount of scratching. He also never scratches in this area when he does scratch. This is the only bald spot on him and it's on a very pudgy area on his chin, it does have a couple tufts of fur coming out of it, could it just have been dragging or something? These things make me wonder, a) is he a sloppy eater? I can't really tell honestly b) could the Baytril and Doxycycline be irritating that area? or c) could his favorite toy have done this? I included a photo of his ball, he throws it around and chews it, but I noticed a couple rough areas on there (you can clearly see them in the photo). I don't see any sores, there are a few teeny pin point size red marks which look like could have been caused by the ball. The photo may be a little hard to see but it was the best I could do. Or does this look like something fungal? I administered the Revolution tonight but I just don't feel like this is mites. I could be wrong though.