Well, my 76 Cheyenne did the same thing. The entire roof. Dark sliver. The selling dealer blamed the mandated EPA primer formula change and repainted it for free.
Now my 2001 white Yukon xl 2500 hood and passenger door are peeling on sheets. No luck with corporate or the dealer. Local "paint" shops want $1800 to strip and repaint just the hood. So, it's duplicolor for me. Bad show GM. You knew all along, stoop by and did NOTHING. I like my truck, but not how GM is not taking ownership for a problem they knew about a long time ago.