Lower leaves of Rudbeckia (black eyed Susan's) have black spots on them. We have had unusual amounts of rain this spring. Could this be part of the problem?
How Should I Treat Black Spot on Rudbeckia
Certified GKH Gardening Expert
Yes, the additional rain is the cause. These plants tend to grow close together, which means there is not much air flow to begin with. The additional moisture from the rain makes them far more susceptible to fungus.
A standard fungicide sprayed on the plants will help clear up the problem. You may want to consider dividing some of the plants if they are growing close together.