When connected to a music sourse, why do I get no vocals?

I hooked one of my Eurolive B210D's to either my computer or ipad and I get no vocals during playback. I have tried using my second speaker and it does the same thing. I connected a small set of computer speakers and the sound was fine, both vocal and music, so I know the output device is sending the signal properly. How can both of my speakers not produce vocals? Last year they were fine, no problems. I have no idea what to do about them. Any advice or help troubleshooting them would be greatly appreciated. They were stored in the attic in their boxes, covered in the plastic and set on the foam inserts that came in the boxes. Could this have damaged the electronic components inside? If so, which ones would have been affected?