On Thursday before we left, Socks began to pound on the shower door, which is his, "I don't feel good!" signal (smart guy; very communicative), and I took him to the vet. Another blockage situation. The vet and I agreed that, rather than overburden our house sitter with two elderly cats and a younger in an apparently precarious health situation, we would leave Socks with the vet, so that they could observe and hopefully get a handle on what the heck's going on here.

We return with an adjusted dosage of medicine, and will see if that does the trick.