Conoclinium coelestinum has some pests that may cause leaf curl. They include aphids and leaf miners.
Conoclinium coelestinum (Ageratum, Blue Boneset, Blue Mistflower, Blue Mist Flower, Hardy Ageratum, Mistflower, Wild Ageratum) | North Carolina Extension Gardener Plant Toolbox (ncsu.edu)

You can look to see if there are pests living on the center core of your plants. If you see in try to
remove them or use an insecticidal soap to help control/eliminate them. White flies are difficult to see on the leaves but may also be a cause of the leaf curl. Look closely at the leaves, back of the leaves and on the stems as well.

The leaf curl in your picture does not give indication or evidence of these pests. Leaf curl can also come from herbicide drift and that can spread over a large area. We have had so very windy days recently. So that should also be a consideration.

There also may be a nutrient deficiency in the soil and doing a soil test may be of some benefit. If you have not done one before the following information should be helpful.

Consumer information on soil testing in Durham

https://durham.ces.ncsu.edu/2020/05/nows-the-perfect-time-to-test-your-soil/

For more information on herbicide drift, I am including the following link:

Herbicide Damage on Flowers | University of Maryland Extension (umd.edu)

You can also bring in a sample of your plant including the curled leaves, stems and roots for our agent to look at for a more definite diagnosis.

Our office is located at 721 Foster St. Durham, 27701, and is open M_F from 8:30am- 5 pm.