Q.Butterfly Bush Performing Poorly
The leaves are speckling yellow all around and the underneath leaves starting from the bush base are shriveling you and drying out and dying, the bush is looking sparse and it was full and beautiful; this happened last year as well but much later in the growing season.
Certified GKH Gardening Expert
It looks like spider mite damage. Be sure to keep the bushes watered, because spider mites love hot, dry conditions. Here is info on control: