Actually, it's more likely that those whiskers were burned through during a derailment... the ends look blued.... When there is a short through the wheels (like derailing on a switch), that contact area is so small that it overheats the wire there, and at least softens it, if not burns through.
But it does not really matter, they need replacing. Is power still being picked up at the axle tips? It's important not to rely on the whiskers only for power pickup, especially if you are not using the skates.