Addi click lace needles discoloured?

I’ve only used this pair of tips for about a week, and now the ‘click ends’ are smudged-looking and feel sort of rough. It doesn’t rub off. Weirdly, the rest of the tips are fine, only the ends which connect to the cords are affected. And looks like the metal ends of the cords I used are a little discoloured too…
I read about using vinegar solution somewhere but I’m afraid to try it out… Any advice please?

This site mentions problems with discoloration of the tips but I wonder if something similar is happening with your click ends?

There seems to be a brass base which may tarnish or react and in some cases a nickel coating to prevent the tarnish and any reaction.
You might contact the yarn store or Skacel to let them know that you’re having problems.