On Jan 18, 2023, Ray J wrote:
My first inclination is to ask If you have reported the issue to the dealer you purchased them from. They need to know. I have worked for several manufacturers and trust me, there is stuff that happens "in the field" that they would like to know and would address if only they knew. But oftentimes they never get the message.

So I'd reach out to whomever sold them and tell them of the issue and ask for their advice. They may offer to send you replacements. In any case, you will have done a service to everyone in advising them of the problem.

As far as "cleaning" the cards, that is a tricky question (no pun intended) and unless we know what the discoloration is, any "fix" would just be a guess. The so-called discoloration could even be below the finish that is applied. So to get it off you have to remove the finish which would probably be even worse.

I'd start by contacting the dealer.

If you want to experiment, with the knowledge you might ruin the cards, likely in my opinion, there really aren't any safe ways to go that won't alter the appearance in my opinion. Fournier cards can be literally submerged in water with apparently no deleterious effects, but ordinary "Bicycles" not so much. Any wet agent like water is going to impact the appearance negatively. And rubbing the cards could be problematic because it could possibly alter the sheen of the finish.

Hope that helps. Good luck and tell us what you end up doing.