My husband and I spent the afternoon at Puss's house. Puss, I'm sorry to say, is really now on the decline. After my discussion with the husband, the kitties were isolated, and it was determined it was actually Puss that is doing the improper bathroom habit. He is also VERY slow, and is not cleaning himself well. The younger kitties have no animosity toward Puss. There is a vet visit scheduled for all the kitties in about a week. Again, thank you all for your suggestions. I'll update after the visit.