We purchased our c1905 home in central Florida 4 years ago. At that time we hired a "pro" to handle painting the exterior. Large portions of the stucco were covered in what appeared to be a black mold. Supposedly this contractor knew what he was doing and prior to painting, the house was pressure washed using bleach. (I do not think a primer was ever applied.) During the past 6 months or so, these "black" areas have begun to reappear. We have scrubbed and scrubbed to no avail. It is now so bad that I seen no alternative but to repaint. I have also noticed other homes in our town (of similar construction) displaying the same problem. Any ideas what this might be? Any suggestions with how to correct the problem?