1) eating too fast
2) stressed

Both. Cats do not like changes to routine, and believe me, they know exactly when food is due! Pinot throws up when we have a pet sitter for both reasons (not all the time), and sometimes does it even when we feed her, but that's usually when a furball is involved. Pinot also eats EXTREMELY fast-she is set on inhale.

It's going to happen sometimes and can't be helped. I hate to sound blase about it, but it's the truth. Smaller bits at a time may help. Your kitties will be OK, honest!