One of my kitties has been throwing up his/her food quite a bit lately. It's been going on for about a month. Maybe once a week or twice a week this happens. I haven't discovered who it is yet - it always happens when I'm asleep or at work.

A week after it started (about three weeks ago) I began switching them both over gradually to Science Diet Sensitive Stomach food, hoping that would help. It hasn't. The puke piles I find are thrown up food - not a lot of liquid in there or anything to make me think they're getting into/eating something they shouldn't be when I'm not looking. They are both acting perfectly normal, but we know how kitties can hide being sick so well.

I am inclined to believe it is Sophie doing the puking, although I have no proof. The reason for this is 1) this all started immediately after I took her (gradually) off her kitten food, about 5-6 weeks ago, and 2) the size of the puke piles isn't all that big (she's about 4-5 pounds lighter than Tito).

This also started occurring when I started free feeding them (see this thread). Could one of them simply be overeating, causing him/her to puke up what they can't digest? Could it be that one of them has a hairball? Or that one of them is sick somehow? Should I take them both to the vet? Start switching food again? Any ideas of what could be causing this are greatly appreciated!! Thank you all!