I'll give you some pointers you should try with him.
Growing dragons such as yours should be offered live insects 2 or so times a day. And they should be allowed to eat as much as they want in those feedings. They can eat a lot of crickets! It's very common for them to eat 20+ each time!
A salad should also be offered every day.
I wouldn't rely too much on the pellets, they usually dont eat them and live fresh food is much better for them.
Of course if they are going to be eating that much, their tank temperature and lighting needs to be proper! For a dragon of your age, a basking surface temp of 105-110 should be provided. You cant use the dial stick on thermometers they are very inaccurate and they cant measure the surface temp which is important. Make sure you have a digital thermometer with probe end or an IR temp gun.
Additionally you want to make sure you are providing proper uv exposure with a good
uvb bulb.
All these items work together to help keep your dragon as healthy as possible!
-Brandon