Dark patch on bricks above bay window on outside of house

[Julia9CA]

House had all downspouts, soffits, fascia, and gutters in roof replaced a couple of months ago. The weather has been bad, but recently we've had quite a few dry and warm days. The dark patch on the outside of the house above the bay window (please see photos) is still there, and I think has been there for quite some time. There are no signs of damp, stain, or damage on the inside of the house.

Is this something that is easy to treat/resolve? If so, any recommendations? Or would this most likely require professional expertise?

 

[noseall]

House had all downspouts, soffits, fascia, and gutters in roof replaced a couple of months ago. The weather has been bad, but recently we've had quite a few dry and warm days. The dark patch on the outside of the house above the bay window (please see photos) is still there, and I think has been there for quite some time. There are no signs of damp, stain, or damage on the inside of the house.

Is this something that is easy to treat/resolve? If so, any recommendations? Or would this most likely require professional expertise?

Trés odd, random stain? I wonder if it has anything to do with the roll joint upstand?