That's weird. Being nearly 2 weeks after they (besides mama cat) were fixed, I doubt it's related to the surgery. Do you think you got a bad batch of dry food? Or maybe they're catching a lot of mice and don't want kibble? Anyway, if they're eating the canned food I guess they're not too sick. Just keep an eye on them and call the vet/clinic if they won't eat anything.
i don't think they catching a lot of mice because before the surgery, they would eat and the food would be gone. they probably tried of kibble or something. i will keep a eye on them.