Yeah the bubbly part is what makes me wonder. I've been told that is an early indicator of RI. Doesn't have to be all thick and sticky. It can also be bubbly and prevalent like your guy. But I mean, bump the temps up a few degrees to get his immune system into overdrive and bump the humidity up some and see if his body clears it up on its own. If it doesn't in a week or 2, I would consider a second opinion like I said.