I've had my Earpods for well over 6 months now & have been extremely happy with them - until now. I've noticed that over the past few days/weeks I've been having to up the volume on my iPod. And I have now just noticed that it is louder if I put my ear up to the 'front vent' or 'rear vent'. If there was more than one audio driver in each bud I would assume that the 'primary acoustic outlet' driver had blown - but AFAIK there's only one in each bud. Any ideas on what the issue is here?