Also if they have munched on any leaves that have dried and fallen off.That's a ton of good information, thank you. We haven't taken him to the Vet yet but are doing a few things to try and isolate the problem. We're changing their feeding bowls to the kind that force a cat to slow down thinking maybe he's just eating too fast. It doesn't seem real likely to me but worth a try. We're also looking into our house plants and have found 2 that could cause the problem. A pothos and a dumb cane. We're not seeing any recent evidence of them chewing on them but they have in the past and even one little nibble could do it. Fingers crossed.