I’m new to pellet stoves, having just had a castle serenity installed in finished basement. Really love it so far. Just curious how much buildup on glass is normal. The buildup I get so far removes easily with damp paper towel. Been 2 days since I wiped glass and and a brown haze most prominent on each side of the glass. Kind of looks like an X-ray of set of lungs. Does this look about normal?