Is there a way to make my bearded dragon grow?

my bearded dragon is a year old and she is only 14 and a half inches tail to tip, and from what I have read and have been told they should be bigger then this, is there supplements that i could dust over my beardys food, veg or insects that will help her grow? or is there lighting or something that can help with this? she isn't very bulky either compaired to all the ones in the pet shop i got her from. and yes I am feeding her the amount thats needed and already giving her calcium etc and she has all the heat and uv and uvb lighting and has a tank that is large enough so no advice about anything else please, just answers to the question