Jargar cello strings have some sort of tarnish on them--help!?

i bought a set of jargar strings for my cello about 3 years ago and havnt got around to using them except for the A--which has some sort of 'rough' spot that messes me up when i shift, and doesnt come off if i scratch it. i also noticed a sort of black 'tarnish' like thing going on on my other strings. tell me, is this normal?