When baking two bâtards or a few baguettes, I've noticed of late the bottom of the bread closest to the left side of my stone is much darker than the others. Almost black in a few spots, as if it was charred.
I have a natural gas oven, 14" x 16" x .5" stone (which is clean and in good shape), and have an oven thermometer on each side of of the stone. The thermometers read the same temperature, be it 500F or 460F. There's always a sheet of parchment between the bread and the stone.