I've come across my first [known] case today, a DVD produced 2011, which I purchased 2016.

Most of the disc's underside is milky and there are some trails like from a worm. Of course the player can't read it, so it's for the bin. 

Sad, because it's also one of many films that I *planned* to view. Luckily it's still available for (re)purchase.

We even have a separate and pinned thread about this matter.

It appears that all types of disc-based media (CD, DVD, HD-DVD, Blu-ray, UMD) do have this same issue.
This also is a global issue and not related to some companies.

However, disc rot and/or bronzing can sometimes be prevented, given the fact that this phenomenon sometimes can get worse in cases of higher humidity, (U.V.)light sources, and even specific temperatures.
It is a chemical process, which when starting, can't be stopped nor reversed.

However, quite a few disc rot issues are more related to the way of making these discs.

Take for example the earlier audio CDs. Chances are that most of these discs nowadays are still in a perfect shape.
But later, most of the time even cheaper processed discs are more prone to rot.

Unfortunately I also have quite some discs (CD, DVD and even a couple of Blu-rays) that have the same issue.
One disc is already been replaced via the distributor, but others I did need to buy again or left it as is.