Sometimes when you’re working with the Healing Brush or the Spot Healing Brush tools close to areas of high contrast, your healing area will get dark smudges on it. Yes, it happens to me too; it’s not just you. In the tool Options Bar at the top, change the Mode from Normal to Screen, and that should fix the problem. Alternatively, you can make a selection that excludes that dark area to contain it. 

This tip previously published in the December, 2020 issue of Photoshop User magazine in Colin Smith’s “Photoshop Tips” column.