DVD was made with organic dyes that are susceptible to disc rot. For a brief time some cheap blu rays were as well.

Now though all blu rays are inorganic and should last about 100 years. Some can last closer to 1000 years.

No, that's missing a crucial distinction. Writable CDs and DVDs used to be made with organic dyes, and yes, with BD-R the new LTH technology is inorganic and probably longer lasting.

But read-only media has always been pressed and then vacuum coated with aluminum. No dyes.

And the main component for both is always polycarbonate, which is organic, and probably won't last 100 years. There were some problems with early DVDs where the polycarbonate was not sealed propery, which led to oxydization of the aluminum layer, that's probably what GP observed. And of course that can happen through degradation as well.

In theory, it's possible to make these discs from glass, which should indeed last thousands of years. I've even heard that some glass music CDs were made for Hifi enthusiasts in Japan.