Almost every night, one of my cats (not sure which one) either vomits or defecates on the floor. I'm not sure if it's vomit or feces. It's yellowish in color and it's mushy and liquidy. Neither of them do this at any other time; it's always while I'm asleep. This has been has been an on/off problem for several months. What could be the cause? I have not seen a vet yet and it would be best if I could settle this without seeing a vet (but I'm willing to) because my mom won't pay for it and I don't have a job. I changed their food several months ago from a cheap brand to Purina Naturals at the recommendation of the vet because they said cheap cat food is like McDonald's for cats. I'm not good with time, so I'm unsure if the start of vomiting and change in food coincided. I think if the cats were bothered by the change in food, they would have adjusted by now. But they're not doing it after eating; it's happening at night. There's no food in the vomit/feces.