Im not sure just how familiar you are with gt's I have grown out more than I can count and have two breeding pairs.. Most juvenile gt's will start of like this and will slowly bulk up... Females at this size will be round and will not have this.. alos he has not been eating to well he is too interested in courting the larger female...
heres a few pics of my 9" male I lost a few weeks back...
before
and after

I have a lot more too show just too lazy to take pics lol