My dear cat Lucy is 15 years old and overweight. She has had stones and currently eats a regimented diet of royal canin s/o urinary health food. She vomits almost everyday, and pees beside the litter box about once a week. Last week I boarded her with the vet while I was on a cruise and she did not vomit or pee outside the litter box a single time. She has been home since Wednesday night and has already peed once outside of the box and vomited three times. I’m at a loss! She is an only cat, and there are no other cats around. My husband and I brush her everyday, play with her, and give her lots of love. The only think I can think of is that it is environmental stress, but not sure what! Any advice?