Lately, I've been having some major trouble with the low notes on my soprano. I can play everything down to low E with ease, but all notes lower than that are very difficult to play, and I get a really stuffy tone. I know it wasn't like this a few months ago. I've tried putting a leak light in it and examining it in a dark room, but all the pads appear to seal correctly, and I couldn't find a leak at all. Any tips?