My inspection home had no fireplace. hmmm???
BUT IT DID HAVE A NEW FURNACE…
Moisture typically turns the shingles white or brown from rust. That has to be soot or dirt. I think the roof is cold and dust/dirt/soot from the living space or attic is plating out on the roof.
YES, that is the feeling i have too… it smacks of a soot halo or shadow, seems like dust plate out - Im still going to refer to a roofing contractor.
More of a building science problem. Still… some roofer have been around for a long time… you never know what one of them might know.
I would say moisture.
Bathroom vents, Dryer Vent or some other source of excess moisture.
I see the neighbors house has the same “ghosting” on the upper most vent. No stains on the other vents though. Lower vents could possibly be a direct vent from a bathroom or kitchen exhaust = no staining…??