I'd keep a close eye on him but it doesn't sound like RI at the moment. Baby ball pythons sometimes panic when they're handled and they can hiss (or wheeze) at you to tell you to stay away. The heavy breathing may also be a sign of panic/stress/being in an unfamiliar situation. I've handled a good number of RI cases and the number one thing to look for is the open mouth gaping and thick mucus. So just be cautious for now and try to increase the heat a degree or two. Should help out.