This is an established, mature bush. I did prune it back last year. I have a full bush of blossoms, but most are opening brown and spent. Thank you
Why Are My Butterfly Bush Flowers Open Then Turn Brown?
Certified GKH Gardening Expert
This is likely a watering issue, to much or to little.
They prefer a deep watering but need well draining soil so the roots do not sit in soggy soil.
Inspect the plants for any signs of aphids or spider mites.
Neem Oil is a good treatment if you suspect insects. It works as both an insecticide and fungicide and is safe for people, pets and bees.
Here is a link with more information.