Hmm Im not too familiar with RI's but as far as Im concerned, you might just be over-thinking things. From what I hear, RI's should show mucus coming from the nostrils, mucousy bubbles inside the mouth and throat, probably a worse feeding response than normal. Random wheezing sounds coming from their noses has happened to me before too and I often wonder about RI's too, but I found that it could potentially be caused by water in the nose, or stuck shed in the nose, or sometimes they just exhale really loud to trip us out lol
If you have kept your temps consistent for the last few months, I wouldnt be too worried. The only thing that I have to say is that you might want to try and boost the cold side to between 77 and 82, anything under 75 is considered unhealthy.