Nutmeg went through a period last year of higher creatinine (got up to 2.1), normal but rising BUN, and low gravity (forget exact number). Numbers weren't that bad, but concerning. Vet suggested her partial raw diet might have contributed , which she'd been on for years without affecting her kidney values.
Put her on a kidney kibble (which she let me know was WAY too low protein for her) for about six weeks, supplemented by home-fixed kidney diet. Laid off all raw meat. Values all changed to closer to the middle of the normal range, and she's back to her regular diet.
Perplexing, but hoping for something similarly short-run for Frank.