Why dont you try some fungicidal soap.

That guy Paul James on TV uses it all the time, and he's pretty organo-friendly

Excelsior

Dave

It is hard to know what to recommend without knowing the pathogen. Can you describe how the leaf is affected more? Are there spots? a coating? totally black? scorched? Can you post a pic?
Are they only affected in one part of the yard? Do you have healthy plants elsewhere?
Personally, if they have a fungus that reappears each year, I would dig them up, throw them out and get another plant. If there is one plant that gardeners try to find homes for, it is their divisions of black eyed susans.

I think I have the same thing.

I haven't tried any fungicides yet, but I am going to give it a try today.

Here is a link that might be useful: Diseases of Rudbeckia

I have some Black Eye Susans if you want some, and want to come to Cherry Hill.

I had a similar thing happen to me. I had a clump, forget from where, and it looked sickly most of the time. My neighbor offered me a clump, so I ditched the one, and replaced it. Looks beautiful all over the yard now.