I just joined here because I'm concerned about my guinea pig. I have two 6 year old guinea pigs. They have always been very healthy. I noticed that Marshmellow looked thinner than usual. I picked her up and compared to Millie, she was really light. On the fleece in their cage, there was pinkish urine stains. I think maybe it could be a bit of blood in the urine. Their urine was never that color before. I wonder if it could be a UTI or bladder stones. There was pretty big white patches on the fleece too. Both of them seem to be behaving normally, still eating and running around. Why could she be losing weight? Should I take them to the vet?