This could be Southern blight (you did not indicate your home area). You can learn more about it and what to do here: https://extension.umd.edu/learn/southern-blight
Or it could be foliar nematodes: click here then scroll to page 7 (this is a large doc): http://www.hort.vt.edu/ghvegetables/documents/Herbs/PestManagementonHerbs_UConnUMass_2011.pdf
That’s about all of our “sage advice” in this case. Hope it helps!
Hi, Katie, Sorry for getting back you so late.
This could be Southern blight (you did not indicate your home area). You can learn more about it and what to do here: https://extension.umd.edu/learn/southern-blight
Or it could be foliar nematodes: click here then scroll to page 7 (this is a large doc): http://www.hort.vt.edu/ghvegetables/documents/Herbs/PestManagementonHerbs_UConnUMass_2011.pdf
That’s about all of our “sage advice” in this case. Hope it helps!