Looks like UV and chemical damage, looks like the top coat has been compromised and now the acrylic is starting to oxidize due to UV and elements. This shouldn't happen for a few years at the minimum if ever, this can only occur if there is a flaw with the top coating used on the plastic or if you intentionally sand it off, no polish or cleaning product is strong enough to damage only that coat, you would notice it on the rest of the body panels too if it was polish or cleaning chemical, once this starts it'll just spread until the entire plastic lens is hazed like the old Nissan Altima and Maxima headlights that prematurely (4 to 6 years) failed and oxidized. Go see your dealership, this is a problem with the acrylic coating that they apply if it is external which is what I can tell from the photo of the reverse lamp.