I have used Northern (Cubex) pellets for many years now and they have always been the best quality I have used. They still burn hot yet they are not as clean burning this year as in the past. Has any other pellet stove user of Northern (Cubix) noticing the same thing or is it a possible stove issue? The glass on the stove after just a little use is full of ash and you can't see thru it. It isn't the normal grey ash either.