I had 3 daylilies last year that did this. All have different genetics and were in different beds and everything around them was healthy. Also they all look good this year. I think it was all weather related since we had a 6 month heavy snow winter and extremely cool wet spring.
I am so glad the plants ( Crossing my fingers as still early here ) are doing good this year. Wonder Of It All, Alexandra and Startle were the affected cultivar.
I worked for the Sheriff Office here for 20 years and you could always tell when it was a full moon as people suddenly had all kinds of problems and very agitated or excited. We all became fervent believers in the phenomena.