It's important to know which leaves re affected.
If that's the only one, then remove it.
Also avoid overhead water. Water at ground level.

That looks similar to what I had, but not quite the same. I had the big spots with yellow halos. But anyways, I had them a few weeks ago, really early. I treated them with fungicide once and pulled off all the infected leaves (about half of them on all 13 plants) and they look amazing now! I used chlorothalonill because that is what the guy at the garden center suggested. I read online that that is a good all purpose fungicide. I think it's worth a shot to try spraying them since it's still early in the season. The parts of the leaves that are affected are never going to "get better", so you can just remove them. And hopefully you can save the rest of the leaves and stop it from spreading. If you've had a lot of rain, be sure to spray after that. Rain is great for harboring fungus.....or so I've been told. This is my first year growing them. I've just talked to a lot of people.