Mine get like that a few weeks after they bloom. It does not hurt them to just cut them all off at the soil level. I have one area which I get those really tall day lilies I will about in August or September just run the lawn mower over them, keeping the blade on high. and that is it. they come back every year going on 20 years now, no issues. and yes, part of planting perennials is to know their life span, or bloom time, and to plant other perennials to take up the void, before and after. so always something is blooming. Right now my Yellow Wax bells and fall anemenes and some phlox are blooming. Of course later variety of hydrangeas blooming now, as the earlier type are just about done. Its all a cycle in planning.