BF Goodrich radial T/A white letters

The TA letters I cleaned with a scotchbrite pad on a die grinder. The word Radial I didn't. The 255/60's on the rear turned brown, the 215/70's on the front never did.

IT IS A DEFECT IN THE TIRE FELLAS !!!!!!!!!!!!!!!!!!!!!!

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I have a tire mix like yours Mike, wider for the back. Same issue, fronts are fine, rear are brown. It's a p*ss off! Can't find anything that says the issue has been corrected by Goodrich.