White smoke may be steam from a water leak, like a head gasket or intake gasket. A cylinder trying to burn water would certainly foul the plug, so I would think the problem plug location, would be the place to look for leaks. If the leak is small, it may take pressure in the cooling system (after warmup) before the condition shows.
Also....if you have moisture in the fuel, you can see this...the white smoke and the fouled plugs. Might want to check...especially if the vehicle has sat for awhile. (if the vehicle has an electric fuel pump, tap a fuel port or remove a line and cycle the pump to drain some fuel into a container to check for water)
anyways, couple of thoughts.