Fothergilla are tough shrubs with little that bother them.
We see the leaf notching, but don't think that is the work of the caterpillar in your photo. It could be weevil damage, but that shouldn't be serious or concerning.
How does the plant look overall?
From just from the little showing in your picture, it looks like the bush is on the thin side.
How deep is your mulch? It shouldn't be more than 2-3 inches and definitely pull it back from contact with the bark and base of the trunk.
Thanks so much for your reply.
The plants look okay overall. They are relatively new.
I will check the mulch.