Genie threw up this morning shortly after eating a mixture of about 3/4 of old food which they didn't seem to like that well and 1/4 of new food (RC Persian formula, which I thought would be good for their hair and hairballs). Could this have caused her to vomit? Or is it more likely a hairball issue? (She has thrown up once before with a hairball, but this time no hairball was there, only food.) Or something else?