Carrie:
It can be a problem here. I'm not sure what it is called, but usually caused by moisture on leaves, moisture in air, and dry soil. You may find the flowers disfigure eventually, and it can be soil related and hang out in soil. But not forever and not always. I have echinacea that do the same thing sometimes.
I highly recommend you get drip irrigation instead of a sprinkler system, a sprinkler system will compound the problem.

GGG

Since we are investing in a sprinkler system to cover almost three acres, I figured I would ask the installer about burying hoses for a drip system. He said it would be too hard to do because my borders are so wide and long and I would have to remove at least 200 plants. I have been overhead watering for years at times during the day that I shouldn't and have never had this problem before and that's what is so weird.

This year, actually, I've started watering at about 630 in the morning, but I guess any moisture on the leaves isn't good.

Now the system will water at 4 in the morning - and I am hoping it will cover all my borders. I can deal with disease better than dealing with getting up early and watering. I may have to switch what I like growing and not do so many rudbeckias since I seem to have a problem that I don't think will go away anytime soon.

I will a stick a couple of drip hoses within the garden myself if they add another spiget close to that border.

Thanks

Carrie