Maybe you could talk to your vet about a different brand of prescription food? I always had better luck with CNM rather than Science Diet. My oldest, Amadeus is on CNM-UR for bladder crystals and he's done really well on it. I'm not sure if they have specialized ones for different crystals. Or maybe it might be an idea to see a holistic vet? I've never seen one, so I don't know much about them.

Good luck.