Jeffrey A. Streich

I have some buffalo nickels that are in a white square cardboard piece lined with plastic and stapled. Then, I have them in another plastic sheet with slots to hold the squares. the coins seem to all have a black look on them. Is this from sweating inside all this plastic? Did it ruin the coins value or can it be fixed? I bought them this way and left them for years.This is my first day on the site here. Hope someone can help, Thanks!