Mt. Airy Fothergilla
Hi: I have three Mt. Airy Fothergilla growing in my back yard. They are full sun part shad. One of the plants, come autumn does not have yellow red orange leaves but has dead or near death leaves over a majority of the plant. It is also the smallest of the three. The leaves are brown and shriveled up. Thank you for your insight.
It sounds as if something may be wrong with the root system of your one troubled fothergilla. They are pretty tough native plants that rarely have any problems related to insects or diseases.
For some reason the root system doesn't seem able to support the plant through the season (assuming it leafs out fully and normally in the spring).
If it continues to be lacking you might consider removing it and letting the others fill in or a replacement with a healthy specimen.