Just in case water has got into the plug area it would not be a bad idea to fill the cavity with wd40 or similar and let it sit there overnight so it might percolate down the threads a bit. I know it's a bit late for you but with all new cars (including my GDI)
I remove the plugs as soon as I get them and re-fit with the threads lubricated with ultra high temp ceramic grease (better than Copperslip). Good luck.
