Severely damaged contacts (MD/Genesis)

[Cyantist]

I hit up a charity shop today. The lady in there is really nice. I fixed a bunch of stuff for her a few months back and now she insists on giving me games the rare times she has them. So today i got Super Wrestlemania, Splatter house2, Buck rogers,and some nigel mansen car game. All the games were mint and cib apart from the fact the contacts are wrecked. Most EA games get a weird green coloured board over time but some normal MD games have the weird colouring too. some also have contacts essentially missing or very damaged. I took some pictures. I have even bothered to test these as im away from home ATM. Im wondering what causes these, what i can do and how i can preserve it.

Using facebook to host it rofl

EA game with damaged contacts
Normal game with damages contacts

Hoping i can fix these as all are mint CIB and even have the wee willy winkies intact