Here are a couple of Gerhard Richter's watercolors:
Here the opposite is true. Almost everything is soft edged.
And here there's a mix of edges that gives emphasis to the hard edged darks. Deciding deliberately what kind of edge you give to your shapes puts a powerful tool in your hands.
Choose a photo from those below, or use one you find on your own, and adjust the edges as you please. You might try different versions that shift which edges are hard and which are soft.