Appreciate some input on spark plug reading

Well I just had to go pull the rest of the plugs and then cut one open. All 8 of the ground straps look the same - they are clean from the tip down to around 0.090-0.100 from the thread body (pics don't show it too well hence my measurements).

Here's a pic of the one I cut open (happens to be #6). Remember this is on pump 93 fuel.

It looks like the dark ring is a tad over 1/8" up from the insulator step. Also know this plug was not pulled at the end of the track but was essentially pulled after driving back to the pits and sticking the car in the trailer.

It should also be mentioned that all the plugs have roughly the bottom 2-3 threads showing darker/sooty.

So there we have it. Perhaps a tad in the rich side? Temps did climb throughout the day from 63 upon arrival to 87 when the last pass was made. And I didn't change any jets as I didn't need another variable! (The car ran 11.140 off the trailer at 63F (455 DA) and 11.162 on the last pass at 87F (1980 DA).