I've had my big normal male do that occasionally, as well as some of the snakes I used to keep. I swear it was like a sigh. Never had an RI problem, and usually it was around shed, I'vd noticed it shortly before and after. Just keep an eye on temps and continue to check for RI symptoms. You should be fine. Don't let someone scare you into thinking he has an RI either, just be vigilant and you'll/he'll be okay
you sound like you know what your doing