His growth doesn't always depend on feeding. It can depend on water changes, food, tank size, etc. If he is in a smaller tank with not many water changes he may not grow as fast. He also is getting bigger, then tend to grow faster when they are small. When the fish gets older it doesn't grow as rapidly.
Feeding him 30-40 of the 2mm pellets should be okay for him.
Feeding him 30-40 of the 2mm pellets should be okay for him.