Ok so my leoaprd gecko has a underadverage size tail for a juvinile whats going on!!?

ok i realy dont understand i gues whats in the tail of the leopard geckos because he eats a normal diet and still doesnt have a nice juicy tail i guess its fine but still a little underadverage...hes on paper towels just switched 2 weeks ago ive had him for 4-5 weeks and he seems to be 6-7 weeks old so preaty young well when i got him he had a skinny tail also and i seemed to put a little weight on it. i guess what i dont understand is that he ate the past 5 days 4 wax worms ik but im trying to fatten him up dont critizize and 2 mealworms and about 3 crickets which isnt bad because what he ate on the 2nd week was terrible maybe a whole 4 crickets then he picked up the eating again maybe hes growing. now i might have fed him to much d3 calcium with his crickets which is herd was a mistake and never fed him calcium cause i thought the sand would be enough but i now understand that is a killer... now i have a bowl of calcium and just started 2 days ago coating all the food with pure calcium and give him a break of the d3. he has temps of 80s day and 70s night. he poops regular with like a occasional mushy poo/ possible runny but thats happen once or twice. He drinks a TON of water every night to everyother day he just chills by the water dish for a long time. so basicallly im asking how i can get a nice fat tail on the guy.