Well, the SP519s are a standard heat range plug and the gap you checked should not have posed a problem, as the factory gap is .055. No supercharger on the car, right?
So, I have no explanation other than I've had mixed success with MC plugs over the years. Obviously, it wasn't a great idea not to wait for the 8th plug, as now there is another layer to the puzzle.
2014 Premium GT, SGM, Brembo, Auto, Tech, Comfort, etc. GT500s, Steeda UCA, VMP auto N/A tune. 100 shot nitrous on BBR tune. Best e/t 11.38 at 120.85
2012 Premium GT, Candy Red, Brembo package, 3.73, MT82, Comfort, Tech, et al. Procal tune, Roush UCA, UMI poly LCA, GT500s, Steeda red bracket, Hoosier 28x10x16 bias drags. Best e/t 11.91 at 115.23 RIP