My perennials have holes in their leaves. My flowers stop blooming.
Holes in Leaves
Certified GKH Gardening Expert
Slugs are the usual suspects when there are holes but no pests to be found. They only come out at night, so they are hard to spot. This article will help: https://www.gardeningknowhow.com/plant-problems/pests/facts-about-slugs-and-how-to-kill-garden-slugs.htm