I have a Harman p61 (manual start) and have been burning Energex Pellets. Recently the pellets have not been burning completely and is burning behind the burn pot (flames are not coming just straight up). I'm a total newb this season. I have had no other issues and this is puzzling to me. I have noticed that its struggling to keep the heat up as it was in weeks prior. What am I doing wrong? Is it just because it's winter cold and no longer fall cool? Thanks for your patience in advance