Undersized Ackie Monitor?

Hello all, was wondering if I could get some opinions on my ackie. I acquired Droma early January in 2016, presumably he (or she, looking more female to me) was already a month or so old before I received him. I estimate he is about 16-17 months old, and is about 90 grams and 12 inches long (would be a little longer, had an incident where he lost a bit of his tail). Based on what I've seen of ackies, that seems to be a lot smaller than normal for his age.

He is housed in a custom AP cage, measuring 4ft by 2ft, by 3ft deep. His substrate is a sand/dirt mixture which is 12 inches deep and is moistened regularly so it can hold burrows. I have lots of cork bark to provide hiding and enrichment. His hot spot is about 140 F and the ambient temp gradients from 90-80 degrees, provided by a ceramic heat emitter. UVB is provided by a 36 inch ReptiSun T8 10.0 bulb. He is very active and goes between basking, digging, exploring, and hiding in his burrows. I feed him mainly dubias (with pinkies/fuzzies as an occasional treat), as much as he can eat in a sitting, but he usually needs a few days before he is hungry again.

I am looking for any advice or comments on my ackie's size and what I could be doing differently to promote growth. Thanks!