Lintel discolouration

[John74813]

Is this something to be concerned with and can I do anything to make it look a bit nicer? The remainder of the house has the same lintels above openings but they are not discoloured. Perhaps something to do with this second story extension that was done a few years ago causing water to go onto the lintel?
Thanks in advance

 

[freddiemercurystwin]

Just looks like water run off, BTW assuming that is a mortar joint in the middle that means there will be a steel lintel and this is just a reconstituted stone head unit. Where does the rainwater go that drips down the doors above? Does that all exit down the back of the metal flashing thing?

 

[John74813]

Ok, thank you! So nothing to worry about then. I would need to double check while it's raining but yes, I assume it just exits down the back of the metal flashing which goes onto stone head unit
Edit: Do you know how I might go about cleaning the stone - some brick acid perhaps?