These dark spots that are staining the painted surfaces are bacteria called Gleocapsa Magma. Surface organisms like mildew and algae are unsightly but not as destructive as some of the more aggressive bacteria and fungus. These algae, molds, mildew, directly decompose and break down any material. The first indication of breakdown is usually paint adhesion failure.
Our drive into this new system was induced by the competition in the pressure washing industry but our education and training has proven that power washing just seems to prune the algae, spread the spores, more deeply penetrate the algae into the surface and make the issue worse over time. Each cycle between cleanings gets shorter and shorter and the algae infestation gets larger and deeper.