Hey Willy,
One of the pots looks like it's got some black googe on it. I would suggest using an old toothbrush and some deoxit, or isopropyl alcohol on both pots and get them cleaned up. Disconnect the midrange drivers, just one wire will be enough. Put a multi-meter to them with the meter set to Ohms and see what the reading is. This will tell us if the drivers are still good and where the issue might be.
Biggles