Late 80s Zincoln Phenomenon?

Most likely it is a storage thing. Where are you keeping them?
John1

Take any penny minted after 1982 and one from pre 1982. Put them outside somewhere on the ground. Come back in a year and the post 1982 coin will have likely rotted away. They just aren't made to last.

to the CCF!

Cupric oxide corrosion from improper storage.

Few people realize the scope of this problem. It's not only BU rolls that are affected but mint sets as well. Large percentages of some dates are affected. While there are lots and lots of these BU rolls the fact of the matter is some dates like the '84-D were very lightly saved. Some dates rarely come with nice surfaces and then they became oxidized.

If some of these dates had the kind of demand that a common wheat has the prices would be far higher. There's a perception that all moderns are common so they aren't collected.

The problem is worst in cents but affects almost all moderns. People didn't save things like clad quarters and the ones in mint packaging are usually ruined because much of it is highly unstable.

A few collectors are waking up to the situation and are starting to snap up nice mint sets. Try finding a 1968 mint set with an pristine Philly cent... ...I dare you. There are almost none. Most are ruined and most of the rest have carbon spots.

I suspect done purposely so people would stop saving them.

As others have said, it's due to poor storage. Just another example of how Zincolns literally rot over time.