After a late frost and my husband mulching, a few of my peonies have leaves that look leeched of color. I don't think it's powdery mildew though. Maybe too much shade? I've attached a picture. It does seem to be spreading, so any help would be greatly appreciated.

If the mulch was not composted, you will need to add nutrients to the soil. As the mulch breaks down, it uses nutrients. When completely composted, the nutrients will return to the soil but in the meantime, use some fertilizer.

I think that looks like some sort of herbicide damage.

Mulching peonies is a bad idea, no mulch should be within several inches of the stems.
Remove the mulch and fertilize, plus adding a bio-fungicide might not be a bad idea.

That looks extreme, almost like the leaves have not photsynthisized — like the way white asparagus is created by covering it with straw. How thick was the mulch, what was it and when did you remove it?

My first thought was also herbicide damage, but not glyphosate: the leaves aren't crinkley. Would a weed & feed on surrounding lawn do that?

Thank you all for your responses. Yes, my husband did mulch and use a weed/feed on the surrounding grass, which he does every year. I guess too heavily this year. I will remove the mulch and fertilize as suggested.

Don't fertilize. Just cut away the discolored foliage to the ground and pull back the mulch. Never feed a sick plant. Check your mulch source. This looks like some sort of scorch, either from the late frost you mention, from gases being released from the (undercomposted) mulch, or from the chemicals on the lawn. Don't overwater, just keep an eye on the plant and let it recover. It may disappear for this year, but will most likely recover and reappear just fine next year.

I'd be concerned about killing plant if I were to cut it back.

Down here peonies get mulched every year with zero issues.

Frost doesn't seem like it should have had any effects either.

Raking away the chemical residue from the fertilizer / herbicide (if possible) does sound like a good idea....
Any chems still on the mulch definitely should be removed.

How close to the plant is the turf?

Probably a good time to remove turf away from the flowers.

I would not removed any foliage at this point. I think this is herbicide damage. I would google what to do as I do not have any experience with this issue.

Herbicide exposure is my thought. Where did the mulch come from? It may have herbicide residue in it. Sometimes rather potent, persistent herbicides are used to kill weedy trees and brush, and then the dead plant material is cut down and chipped up and may end up in a mulch pile. Grass clippings used as mulch can also have herbicide residues. I know that one chemical used in lawns is Tenacity (active ingredient is mesotrione), which causes weeds to turn pinkish or white in color.