Aureobasidium microstictum causes reddish spots with yellowish margins that often result in brown streaks down the center of the leaves. Usually this leaf disease does not cause the death of the plant.
Don't confuse this disease with the relatively new (and much more important) disease called daylily rust, which is caused by Puccinia hemerocallidis.
Fungicides and sanitation are helpful. However, if you are willing to accept poor aesthetic appearance by late summer, no treatment is needed. The plants will survive without any fungicide applications.