It's very likey you could have had a little bit of water rolling around on the bottom of the tank since it's heavier than gas, and by letting your VX get so low it managed to get into the fuel line. Keep some 90% or higher isopropyl alcohol on hand to put in occasionally as that's the same stuff in "water remover", just much less expensive.

If it would have been the plugs you would have seen an immediate difference. Don't forget to note the date and mileage info in your maintenance log for the plug change!