Answer: Based on your description it is possible your peony blooms are suffering froma fungal infection. Botrytis blight is a fungal infection that can cause discolored buds and blooms. Usually, in addition to the browning, you will see gray fuzzy growth on them, and buds may also fail to open. Botrytis occurs under certain weather conditions. Deadhead the affected flowers and put them in the trash. In the fall, clean up all of the peony stems and leaves and put them in the trash as well. This should help limit sources of reinfection.
The other possibility that comes to mind is that peonies usually only bloom for about a week. Then as the flowers age they naturally turn brown and dry up. Again, trim off the flowers as they fade and in the fall clean up all the peony debris. This is a good practice to prevent any pest or disease carry over from year to year.
I hope this helps.
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