Since both channels are fed by a single amplifier crossover setting and the tweeter is still functional, the problem is likely within the speaker.
There are two probable causes within the pod; the midbass driver or the passive crossover. Since the only series component on the passive lowpass filter is an inductor the issue is unlikely to be a board component. But it could be the lowpass to speaker connection inside the pod. So take a peek inside. If nothing there is revealed exchange the drivers within the pods which will certainly isolate either the midbass driver or passive crossover board. You should be able to measure DC from the crossover input to the crossover lowpass output. The DCR of the midbass driver should measure 4-ohms or a little lower. If the midbass driver is siezed or the voice coil reads 'open' then it would be the driver. So with a little inspection, a simple swap and the use of a basic multimeter you should have the cause.