What concerned me was the bubbles coming out of his mouth which could be from a URI. Please don't feel dumb about misting in the tank, you didn't know. The 18% reading that you're getting now is a little low. So if you do get a reading of 30% and up to the high 40's, that's even ok. When it goes over 50, then there is reason for concern. When you mist in the tank, it raises the humidity way up where it really should stay at an even reading.
It does sound like he is getting ready to shed his beard, sometimes they even stretch their beards out in the morning, kinda like beard exercises.