What can be destroying my yellow flowered buddleia
Some leaves have holes, lower foliage is dying off and some large shoots break off at the node. Leaves are very patchy with pale and brown sections.
This article suggests some possibilities: https://www.gardeningknowhow.com/ornamental/shrubs/butterfly-bush/brown-leaf-spots-on-buddleia.htm
You can take some samples of leaves and stems to the Extension Service, they should be able to tell you exactly. This link will help you locate one: https://www.gardeningknowhow.com/extension-search/