Yeah sometimes a FH can grow just a bit slower then others. I've had the same thing happen personally. Kept 2 female FH from the same batch of eggs and after 2.5 years 1 of em had reached 9in while the other is currently stuck of 5in. Both of em have the same parents and were born together but ended up looking nothing alike each other.
Btw yours seems to have a bit of a gut on him, could be from over feeding or he just ate before the pics were taken, but if it's the prior one I would suggest fasting him atleast once a week. It helps em stay nice and lean while also keeping em hungry enough for more food/treats.