Check your wiring on the subs. One sub may have it's wires out of phase which will cause it to not move much at all. It will move more though because the other sub is causing it to. Take the subs out and inspect them. There isn't anything else we can say until you get off your *** and try some things on your own.
just because their "new" doesnt mean that they cant have a mechanic or voice coil problem straight out the box, you can have a problem with any mass produced item.