I sorry to hear Luna has problems again. My suggestion was going to be S/D or C/D, but you obviously tried that. It was very hard not to give Fister anything else when he had UTI, but the vet said, "Not even one or two shrimps". Well, as you know, that didn't work. He still eats C/D and likes it. Sometimes I let him have S/D, he prefer those because they contain more fat and probably taste better. There are also another one which you can buy from vets, but I can't remember the name right now. (it's not Prescription!)