My pellet stove runs about medium thermostat temp and auger feed when I first start up. Typically, it runs for about 10 minutes then slows down to the low temp speed setting I have the thermostat set on. A week ago I used a different brand of pellets (which may just be a coincidence) and the stove won't reduce to the lower temp. Now even when I put my tried and true 'packsaddle' pellets, It still runs at medium. It get's hotter than heck in my house! HELP! Any ideas?