A lot of reptiles slow down their growth process because they aren't getting what they need and if they grow in spite of that they'll have terrible deficiencies. Is he eating the correct foods. Do you have adequate uva and uvb lighting for him? Are you giving any kind of vitamin supplement? Is the tank big enough for him to have a warm spot under the basking light and a cooler spot at the other end? Is the ambient day time temp between 84 adn 88 F with a basking spot between 90 and 95 F? Is he eating a variety of live prey, lots of greens, and some other veggies and fruits? Does his enclosure have 60 to 80% humidity with a large enough water dish to easily swim and bathe in? If not it could answer some of your questions.