Pastel Problems

[MitsuMike]

Ok so I am having issues with my Pastel. I worry because he is my First snake and is normally very nice and I have never even heard him hiss before yesterday.
Here is the situation:
About a month ago I had all my snakes on Aspen bedding and noticed it was VERY dusty after about a week or so. Changed to Repti-Bark now (love that stuff) But while on the aspen I noticed that he was breathing hard. Like I could hear him exhale heavily (well heavy to me because I normally don't hear them breathing).
I have been constantly checking him for an RI but nothing shows up. No mucus no nothing. Temps are spot on (on a Ranco and just bought a Herpstat Pro for the collection, incubator and babies) and humidity is around 45-60%.
Yesterday I was "petting" him while I took him out and he make a heavy exhale and/or hiss but no striking position or anything and what not. So I checked him out closely and still no mucus or bubbles. Opened his mouth and it look normal and fine (color was a like pink to white color). He doesn't make any popping sounds and has been eating. Has it just got grumpy with age?

[PghBall]

Balls will hiss when they don't want you messing with them. I have two females that do it on a regular basis. Neither shows aggression, just lets out a loud hiss and then gives in lol. I'd say he's just being a little grumpy from what you explained.

[MitsuMike]

Yea he did just give in. haha But it's strange because I have had him over a year now since he was a month old and he has never done this. NOW my fire is a grumpy butt and love to bite me every chance he gets, but I find it cute because he is small (compared to me).
But yea this whole RI thing was throwing me for a loop. My husbandry is perfect, maybe alittle lower humidity (45%) in some tubs but nothing lower than that. And my snakes never see any temps below 79.