Your cat may not always need UTI food. You just need a food the cat can digest that doesn't hurt them. Many vets will give you a specialist food because this is what works best in most cases, but not always, switching to limited ingredient foods, or senior foods can have the right combination of ingredients to keep the vomiting in check, as well as the UTI.
A Switch in cat food can take from 2 weeks - 1 month to show itself so just because the cats are fine now, it does not mean than down the road the UTI will not return. Keep an eye on your cat's health.
Does the cat behave normally, or does it hide away from you? A cat that hides is a sick cat!
Check the litter tray, make sure the cat is peeing and pooing frequently and normally! You know what a UTI looks like!
Check the coat of the cat and behavior. A glossier coat and more energy will show that the food is giving the cat more nutritional value than before.
What I would do, is watch the behavior of the cat, I have had a sick cat with IDB can a food change can cause him to start pooping blood, so I am always very cautious whenever I have to switch. Whenever I am in doubt just call the vet and ask, you won't need an appointment, just a call, and they can put your mind at ease!
