Dynastes Grantii Lack Of Growth

I had a general question regarding the overall growth of a Dynastes Grantii larva I purchased back in February. He (That is to say HE because I don't actually know his gender on account of him being in at least mid L2) hasn't grown at all in the time I've had him and I'm encroaching on a one year birthday if you will for the little bastard but he's still the same as when I first got him. I bought him from Coast2Coast, I bought several more after. (Which I've since sold.) A few of the friends I gave some away to friends which notice much better growth in theirs. I was wondering if it may be an issue with the size of his enclosure? Each of my friends have kept theirs in the small tupperware I gave them in, and they've grown much bigger than mine. Mine was in a small tupperware for a little while as well but I moved him to something like the picture provided below(Minus those black bars). Is it because I sized him up too early? Does he need to be moved back to a smaller enclosure?

Grantii takes a LONG time to reach adulthood, I had a female that took two and a half years excluding reputation and pupation. If you’re using one of those enclosures moisture can be hard to maintain constant, make sure there is enough humidity in the substrate. Good luck keeping one of the largest beetles in the U.S., moisture is crucial.