If peonies are planted too deep, do you wait until Fall to dig them up?

My peony plants have probably been in the ground for 2-3 years, and three out of the four plants are blooming. The last one has lots of foliage, and looks healthy, but no blooms. They get lots of sun, 6-8 hours/day. They have been fertilized. I figure the only other option is that the plant is too deep.