My adult 7 foot darwin was like this, he has been a bit whistly/wheezy for a couple weeks. he had a very big feed and the day after he seemed to have a weird mouth, it was red and irritated inside and there was mucus, and one of the sides of his mouth was drooping, the bottom 'lip'. There was a more than normal amount of saliva and some white mucus. I put him in an isolation container and spiked up his heat, expecting a vet trip in the next couple of days. however the next day the saliva and mucus and mouth redness was gone, so i assumed it may have been the large feed he had that had done something to his mouth from stretching more than normal.
He is still slightly whistly and i still have him in the isolation container with around 32+ for heat, im thinking his enclosure was getting too cold and he may have RI from that, as he only had a heat pad due to faulty light fittings (thanks to the guy who built the enclosure incorrectly i assume)
anyways i will be taking him to the vet within a couple of days, when i can get an appointment, but i have noticed he is now going into shed and after reading your comment i was wondering if the wheezing/whistling could be from this...? i have never heard of it being a symptom of shedding...
(Sorry if this is hijacking the thread)