Arcing across coil terminals

Fresh plugs, .035" gap. New wires. Just cleaned the cap contacts. There is discoloration all over the coil boot though, looks like burn marks from the arcing. The car ran like a top right after the new plugs and cleaning the cap. This problem just developed after a couple days of running great. Daytime temps are in the high 90's though, not sure if that is related. The coil and distributor are getting very hot, especially after shutdown when water stops circulating.
You mentioned new wires. I see the new wires (grey colored) and a not new coil wire (yellow) with discoloration at the coil end. Just sayin'