Gracie had a patch in that exact same spot for a couple months. Putting her in a shirt helped, but I finally had to resort to a Cytopoint shot because I was worried that it would get infected (the vet did check for mange and a bacterial infection, but both were negative). Personally, I think it was from the "pinestraw" mulch that we had just laid, but I'm not certain.
I fed Gus Fromm puppy when I first got him. He liked it, but it seemed to give him bad gas, so he wasn't on it long (mine are now both raw fed).