Oh, ok, well that I know how to explain
It's not a glitch, it's completely normal, because like any game really Bandai doesn't want you to rely on the fact that the Baby Food is going to be there forever, it's like... an emergency food because your Tama can get famous and make loads of money. But before that first Debut, there is some trouble.
So, basically, it's an "in case of emergency" kind of food, really, if your running low on the money, got for items like Bread in the shops that are 100GP and fill one heart each, so fill the two with baby food, and them the next two with the Bread or something.
Various foods will fill more happy hearts, like Beef Bowl fills 2 hearts, and the Mega Pizza will fill all hearts, happy and hungry, but it's rather expensive.