Calling All Spark Plug Experts, Opinions on these pics.

The drivability issue surfaced after about a week of damp weather and not driving the truck, so that would point to wires. The wires are all the same 12" long since the coil packs sit on the valve covers directly above each plug. But who knows if the wires were degrading how long they were delivering low voltage to the plug. Other suspect is weak coil packs.

Any comments about changing the heat range of the plug?