It's possible it could be gas, but watch out for other symptoms--wheezing, bubbles/mucus from the nose or mouth, open-mouth breathing, swollen eyes, lethargy, refusal to eat. RIs are often caused by temps that are too cool as well as drafts/breezes. A water temp of about 78F is OK for a healthy hatchling. If ill, bumping up the temps a bit to 81-82F is often advised because the warmth will boost the immune system and help him fight the infection. If you do see symptoms, take him to a reptile vet for antibiotics.
Turtles often eat their own poop, so if he's eating and you don't see any, that's what he could be doing.