Without doing testing, that looks like Cladosprorium. Material was probably went and the mold is growing through. At this point, it is going to either be a strip/mitigate/repaint…or hit with fungicide, top of the line exterior mold resistant paint and hope. I’d suggest getting a calibrated moisture meter into that wood to make sure it is not wet from inside from a ventilation issue. Painter probably also has some liability if they painted it wet and didn’t check the material moisture.
