Automatic Litterbox Central

After years of troublefree use of Tidy Cat Multiple Cat, the formulation changed a few months ago. Now it is labeled "24x7 odor control" Its still in the yellow box with the red highlights, but it no longer works. The boxes (both the manual boxes and the LitterMaid) are gumming up with large soft clumps, sometimes with standing liquid on top. Figuring that Purina had just cursed me with a formula change, I tried a number of other brands, mostly shopping the higher price stuff. (tried wheat based, and a few premium brands, etc) The verdict: they don't work either. Has anyone else seen a sudden decrease in the quality/performance of Tidy Cat?

If not, my only guess is that one of the cats is suddenly drinking considerably more water and that is the cause. (Last week we noticed he's frequenting the water bowl more often, and is losing weight. Its worth a trip to the vet but it seems odd that one cat could mess up the entire litterbox system in the house (we have 5 cats total that have shared 2 littermaids and 2 manual boxes for years without issue)