PLz help my bearded dragon has a lot of issuies!?

Plz Help!!! i got my beardie in june. At first he was very active and his coat of scales was nice and clourful. it is now december. When we first got him we used a uvb bulb as a basking bulb. Then yeterday we finally learned that that is not the basking light so we bought him another dome and a 100w bulb considering oour cage is kinda tall. It has een almost six months and he has barely grown a centimeter. I feed him daily, he eats his veggies and calcium. I am mostly concerned because after about two weeks of being with me. Instead of the light brown coat with white at te bottom. He is now VERY dark brown, almost black with dark brwon and on his belly and beard he has a pattern of black lines. I dont know what to do to get him back to his clour and make him grow PLZ HELP. I feed him crickets, carrots, Romaine lettuce, juvenile bearded dragon growth formula with fruit, natural bearded dragon with added vitamins and minerals, calcium, sometimes cactus treats, and thats it. What ami doing worng, PLZ HELP ME and CHAKA!!!!!!!!!!!!!!