The results from the vet are back and Gwen has an early stage of kidney disease. It's very treatable but she doesn't even need medicine just yet. Right now all we need to do is get her onto a low protein diet. It's fairly pricey stuff so even though it would be safe for all the cats to eat it we are going to attempt to feed it just to Gwen. This should make her stomach feel better and she might even gain weight. I popped out this morning to pick up a bag before yoga class so that we can start her on it right away. It's by the same folks that make our current cat food so we are hoping we won't have any trouble with the switch.