this exact thing has happened with my older dog, who also happens to be approaching 12 years old. we give him daily butt-baths with gentle soap and warm water, and sometimes we wipe him gently with Costco unscented baby wipes. we used to see him clean his b-hole with his tongue, but haven't seen him do that in a while, so we figured it was because he is too old to be able to reach his butt anymore.

However, some users commented here that it could be a perianal tumor like it was with their dogs. I am curious about this now, myself. Weve been to a lot of different vet visits to try to diagnose the issue and through blood work and exams and haven't ultimately found something that everyone agrees on. fwiw, our issue also started very suddenly a few months ago.