Sudden weight gain

My Poodle Kitty has gained a noticable amount of weight in the last few days, and I'm a little worried, since she was already a tiny bit chubby. Could this be due to the stress of a new cat in the house? We broght a new girl in about a week ago.

Edit: She is spayed, anout 8-9. The new kitty is 13, and they are both eating food for older indoor kitties. And a call to the vet will be made.

stupid ? is poodle spayed?how old is poodle?

Is she eating a quality senior food?? wt gain in seniors is common , not that fast ... I do advise a call to the vet.. is the new cat a kitten on kitten food??

I'd recommend a vet visit. It is possible (though not likely) that an apparent sudden weight gain could be a sign of FIP. She's probably fine but a vet visit will rule out any significant problems.