What's going on in this mint set

What's going on with these 2 coins?
They are still sealed in the mint set but they look as if they are burned or scorched. Around the black burn spot is amazing rainbow toning but I'm puzzled.
What say the experts?
Like I said the plastic doesn't look to be tampered with or glued back together and these are from 2 different mint sets a 88d and 95d
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Comments
Looks like it may have gotten water or something in it.
Collector, occasional seller
It looks like heat damage of some kind to me.
pmd of some sort. Don't know the source but probably does not matter as both coins seemed ruined.
bob
In that case, it was probably very hot water damage....
It's just weird that it's the only coin in each set that has issues. Never seen it before
HAPPY COLLECTING
I bet there is a pinhole in the mylar.
Pinhole and poor storage.
I was thinking the same....pinhole and moisture got in.
Yep... the last three posts nailed it... there is a pinhole in the mylar....and that allowed the hostile envioronment to enter..... Cheers, RickO