If he has stopped growing then you can try a pellet-free diet. Some bunnies do fine, some do not. From what I have seen on the forum, most (not all) people who go with a pellet-free diet do it because their bunny had an issue with eating pellets. This can happen, but it isn’t common. Otherwise, most people feed their bunny at least some pellets daily. This ensures that their nutritional needs are met. If you are able to give your bunny a variety of veggies and they eat A LOT of hay (which they should anyway) then you can give pellet-free a try and just see how he does. If you notice him losing weight, etc. then you might need to rethink your approach.

I have 2 buns that I feed a pellet free diet.  We have been pellet free for 5 or 6 months now.  My female rabbit would go insane for pellets and wouldn’t eat enough hay, she was also getting quite chunky so after a lot of research this was the path I chose.  The problem obviously with pellet free diets is to ensure you provide all the necessary nutrients pellets were providing.  That includes fat.  I give my buns alfalfa hay as well as other varieties and I also add in a few black oil sunflower seeds a couple times a week.  I grow wheat fodder which they get a small piece of each day.  Fodder is incredibly nutritious.   As much variety in leafy greens as you can and some added veggies and the occasional piece of fruit.  You can be a bit more generous with the veggies then you can be with a rabbit in pellets.  Its really essential for different minerals and vitamins.  Try for a good colour mix of safe veggies.  I also forage what I can through spring, summer and fall.  Winter is a bit more difficult because its really cold here in Ontario usually but I can usually find rosehips, twigs and barks from safe tree varieties.  I’ve been monitoring their weight.  My female lost her extra pudge and they are both a healthy lean weight with beautifully shiny soft coats.  I keep an eye on poops as they are the best indication if there is a problem.  My vet says both are exceptionally healthy.  As long as you are providing all that pellets were providing your buns will be healthy and happy.