Water on my spark plug

Its hard to say without doing tests. A valve spring to fail is odd! Used to see it on older cars particularly if the car had previously badly over heated. Moisture on a spark plug, could it be fuel? Is the spark plug getting ignition? If it were not fuel would foul the plug? Could the plug be getting oil fouled? Whole different issue. If the plug is fouled due to coolant getting on the plug the head gasket would have failed or a crack has occurred to the cylinder head or an intake gasket perhaps is letting coolant into a cylinder. A chemical block check or cylinder leakage test would show head gasket failure.