This is a well documented issue with 2016-17 19in GT wheels. There is a thread or two here on the forums with many users having reported the same issue. Thankfully mine were still under warranty when they started peeling... Mazda dealer replaced all 4 no questions asked. The replacements however started peeling as well a year later. Your only option at this point is to have them powdercoated or painted. Those can't be fixed or touched up.