Answer: Peonies seem to do most of their growth early in the season and then slow down; this past summer was very dry and this too could have had a negative effect on newly planted plants of all kinds. It is also possible that growth slowed due to improper soil preparation at planting time and there is less than optimum rooting. So, based on your description it is difficult to know if the events are related, or not. If you applied the Miracid according to the label instructions, I don't believe an application (or several) would harm them. If you overapplied it, just as with any fertilizer, you might have caused some damage. With the leaching effects of rain any effect it had on the pH should diminish, and any foliar damage will be moot by next spring since the plants are deciduous. The best thing to do is to make sure they are well watered through the fall and again next summer; you might give them a top dressing of compost and perhaps an early spring application of a balanced fertilizer according to the label instructions. Several inches of organic mulch placed around but not over top of them would also be a good idea. I hope they do better for you next year.
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