I do alot of reading actually before I post to here if I can't find something then I'll post I have one the same age that is twice it's size and same type
to be fair you didnt leave any information about your plant
you just asked what was wrong with it
you left us no indicators you have several other plants with same strain that are not stunted growth
its pretty good to include all your information no matter how relevant or irrelevant you feel it is, that way we can help you
your plant looks fine and healthy to me, dont create/see problems that arent there
it maybe stunted but i have no other information to go off of so until we are given more info i cant say for sure