What's your question? Ask

If it was very early morning the spray shouldn't have burned the leaves. But if it was later in the morning when the sun had been shining, there could have been some damage. Were all the instructions followed on the application of the fungicide as to how much and when?

When leaves curl up, the plant is under stress. Although ninebarks don't need much pruning, I wouldn't think that caused the leaves to curl up and die. It seems to be related to the fungicide application. Fungicides are better at preventing a problem than curing it and are typically applied in cooler weather.

If the stems are dead (you can scrape off some of the stem and if it is green underneath, they are still alive), you can cut those back to the ground. If they are alive, let the leaves drop off and remove them from the ground and discard them in trash. Then during late winter, cut the stems back to about 1 foot from the ground.

Hopefully, it will releaf in the spring, if not sooner.

https://www.gardeningknowhow.com/ornamental/shrubs/ninebark/growing-ninebark-shrubs.htm

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm