GQ TB42 runs well but has one corroded sparkplug

[mudski]

Have a look here
https://www.onallcylinders.com/2012/...r-spark-plugs/

Thats handy Phil. I would think if there was corrsion on all plugs, whats on that guide would be it. But only on one plug, gotta be something else.

Would a dodgy lead possibly cause this? Or help with corrosion..