Possibly, but doesn't the pattern look like spray paint? If there were deposits downhill from all of the upper story walls, I would chalk it up to weathering paint, especially if it was in lines that aligned with drip edges, but that's just me. I think a little test with winded or simple green to see if the stain migrates would be a quick test, and if that doesn't shift it, a little solvent.
All the best,
BG