A lot of it could have to do with genetic factors. I mean, I have beardies mainl fed on pellets, and I believe one of them at that age was around 16 1/2 inches (I don't have my records in front of me). Another that my friend fed on pellets and can o crickets that I am now taking care of was the same size at age one year. At about 10 months, the first of the two dragons I spoke of measured at 17 inches. Both dragons came from the same breeder. The smaller one came from a line that doesn't get as big as the other one. If you are truly concerned and have any reasons to suspect parasitic infection and you have not yet ruled this out, it never hurts to find out.