What could be wrong with my Meze 99 Noir

Hello.

I don't remember exactly how it happened, but I think back in late November - early December I got caught in a drizzle here in Berlin while wearing my Meze 99 Noirs, not sure if it matters, but I think it was coldish too, 2-3 C. If I remember correctly, the issue did not manifest itself immediately, but after a few days, and the issue is... okay, so with normal, equal channel levels, like in the first picture, I hear slight metallic din in the background, music playing, but the vocals nearly non-existent, really low - on iPad, iPod, MacBook, does not really matter. When trying to watch a movie, I can hardly hear the dialogues, only when it gets really emotional and loud, people shouting, - only then it begins to break through.



When I change the settings like on the second image, I can hear the dialogues all right, but the din becomes more pronounced too.



I want to give the headphones to a local hi-fi repairman, but thought I'd ask the community to have at least some understanding of the situation - maybe the Mezes are beyond repair.

Appreciate your advice. Thanks in advance.