Help! I have had a peonie in my front planting bed for 7 years now. It has bloomed right on schedule in late April every year.

Due to the unusually warm weather in western washington state this past winter, we have a large amount of weed activity to deal with. After three solid days of weeding and cleaning up our planing areas over the past weekend, i thought i would try a chemical to keep future weed growth in check for the summer. I applied Casoron granules and another weed control agent, Preen, around these areas. I didn't put any around or on the rising peonie shoots. However, the area in which the peonies live is surrounded on two sides by corners of the house.

Now, in the 24 hours since i put down the casoron, the peonie shoots and buds appear to be wilting and turning brown/black on the tips. I checked the area again, and there is no casoron or preen within at least foot of this plant, but it appears to be suffering.

What can i do??