Butterfly Bush is yellow and dropping leaves
The scorching on the leaves of your butterfly bush suggests a problem with water uptake -- possibly due to a root or stem problem. Root damage can occur in soil that stays well for too long (such as during the recent heavy rains). It looks like there is also root competition with the groundcover that is planted below. Also, was any type of salt applied to the driveway in the winter? Were any chemical products used around that area? Had you applied any fertilizer?
There is nothing we can recommend that would be curative for the symptoms you see. You could cut the shrub back and see if the plant recovers next season.
Butterfly bushes are a problematic plant because they have become invasive in wild areas (due to the dispersal of seeds beyond landscaped gardens). With that in mind, you might want to consider replacement with a different type of plant. https://extension.umd.edu/hgic/butterfly-bush