This is not a disease. This is insect damage by a psyllid... actually, the nymph. This is a Rudbeckia Triozid called Bactericera antennata.
They attach to the leaves of Echinacea and Rudbeckia and, as they feed, the insect injects its saliva and that causes the ink-like staining. Badly marked leaves, like the two you chose for the photos, should be picked off and destroyed. Burn them or bury them. Spray the rest of the plant with a product containing cyfluthrin, bifenthrin, Malathion or Orthene. Cyfluthrin is particularly long lasting. It can be found in a carpenter ant and termite spray carrying an extended label for ornamentals.
Spray with a pressurized tank sprayer, especially the bottoms of the leaves. Avoid flowers because any of these pesticides will kill pollinators. You are basically protecting leaves. This is not a cure. There is one generation of this psyllid a year. Next year, begin spraying BEFORE any damage is expected. Timing is everything.
Thank you for your answer... Im assuming that there is no, less "chemical" option to this.. would an oil spray smother them or will that damage the plant? Robbin
Using a horticultural oil will burn then plant to the ground. Oils will destroy the plant.