I didn't notice any significant weight gain with any of my cats until they got to 5 or 6 years old. They have enclosure access so they're pretty active. Having said that, they're all pretty chunky too.
Just keep an eye on them and see if their appetite changes or they start to put on weight. I doubt it will suddenly change when they get to a year old.
Just keep an eye on them and see if their appetite changes or they start to put on weight. I doubt it will suddenly change when they get to a year old.