What causes black spots on oregano and also on spearmint?
Certified GKH Gardening Expert
Are they in the ground or in a container? If they are in a container, it is likely black spot fungus. Treat them with neem oil. Here is more information on neem oil: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm