Since early this week, Whitey has acting like has he has trouble using the litter box again. This has included useless trips, and even urinating in the sink in his bathroom. This indicates litter box anxiety, but in our ever fastidious feline did at pick the easiest place in the house to clean up after.
So it was off to the new vet, and after they couldn't get a sample they sent home the required tools (a small litter box and fake kitty litter) for us to collect one.
Now the results are back, and at least he doesn't have any new infection. He may have irritation which the new food will help control, and which we could give him anti-depressions to act as anti-Litter box anxiety meds. However, we want to hold off on the latter as long as possible.
Update a week later; he seems to be settling down without drugs.