A few days ago while I was cleaning the stove I noticed a build up of soot in the burn pot. It was really hard and I had to use a screwdriver blade to clean it off. The next day my wife asked if I noticed how the exhaust color had changed from clear to a white smoke. Also its not really putting out the heat like it was. Granted the temps outside have plummeted but the room temp. is only 60 directly across from the stove and that is on 5/7 with 4/4/1 across the bottom. Any ideas as to whats going on? Also these are the same pellets (AFW) we've been burning since mid last year. Its the same ton we've been burning for awhile so I don't think its a pellet issue. Thanks for any advice.