The black stuff,
oil above the sparkplug seat is probably valve cover leaking. Try the spray bottle test, plug reinstalled, with the engine running spray water on the plugs and wires. In the dark/garage lights off you will see the sparks jumping off the plugs, or take a jumper wire ground one end and move the other around the spark plugs and look for arching. Looked at the plugs again and I dont see any carbon tracking.