I purchased (4) HUMMINGBIRD SUMMERSWEET shrubs in June of this year.
There are planted in excellent soil (ph about 5 -> 5.5) facing the
|Unfortunately based on your description I am not certain what is happening to your shrubs. These plants require an evenly moist soil and in my experience, in hot summer areas do better in morning-only sun than in full sun all day. So part of what you are seeing could be related to transplant stress, or just as likely, especially since new plants are not fully established and rooted and so are prone to drought/heat stress as a result, related to the weather conditions. This plant is relatively pest and disease free, however stressed plants are sometimes subject to this type of problem as well. I would suggest you work with your local professionally trained nursery staff to determine if is is essentially weather related and/or if you should consider transplanting them to a more favorable location, and/or if there is something else at work such as a fungal infection. There is also the possibility that they have somehow been overfertilized, which would cause foliage symptoms, or even an adverse reaction to the spray. You might also consult with your local county extension. If it is something that requires a chemical control, they will have the most up to date information on what to use and how/when is best to apply it.
I'm sorry you are having trouble with them, these are great plants.