As @loccdor stated above, or there was a mix up. Japanese sellers are very good about customer service. Anytime I had a problem they always fixed it pronto. Japan is a high trust society and as a whole have very high standards.
It could be any level of contamination with oil or dirt on the metal prior to painting - that makes it susceptible to reaction with moisture - essentially, the metal is "rusting" under the paint.
The issue you have is that lens is not what was shown in the photos.
That looks like Schneiduji that turned to the plague. Never seen one that bad. Probably a total failure of the paint. Life is short. You are doing the right thing.