Lino on floor has dark spots eminating from shower pan. Testing showed it as common mold but with the amount of discoloring I'm concerned about the cause! I remodel the plumber found a broken drain about 2 feet below floor level and used a coupling of some sort to reconnect. Should we be concerned about that coupling failing after several years use? If it has failed and the ground gets wet after 2 showers daily could that be the cause of the moldy spots under the lino? We presume a plumber would be the one to call to look for cause but welcome others' suggestions. Pan itself has some discoloration as well.