Hard to tell if something is eating it because nothing is there now. You may want to check at night when most nocturnal insects go out to eat.

The amount of wilting does not appear to be much on the pics. Usually wilting is normal and common in Year 1 (until the plants get established). Windy days can make things worse. The best you can do is maintain the soil constantly moist -not wet, not dry- as best as you can and to maintain mulch, 3-4" up to the drip line. The mulch will maintain the soil moist longer, minimize evaporation on windy days and protect the roots in the summer/winter. Some of the pics show areas where I would add more mulch.

Curling can occur as a result of winter, fungus or an insect such as the hydrangea leaf curler insect. These insects stop by at night usually so spot check several times thru the day/night. Check the bottom of the leaves and under the mulch.

Make sure you water the soil and not the leaves as this can promote powdery mildew, which can cause some curling.

I don't know if it has anything to do with the wilting hydrangea, but by looking at your pics, the grass around the healthy one is lush & dark green, while the grass around the wilty one looks yellowish and bare patches. Maybe something is eating at the grass roots and also the hydrangea? Grubs?

That is an excellent observation, Tario! The problem there is we just had our house built a few years ago and there was a drainage problem in our backyard. Our "brilliant" builder only sodded what was absolutely necessary, so the grass around the healthy one is thick and lush sod, and around the unhealthy one is grass grown from seed they laid. The plants are to the left and right of my deck steps, so you can image how close in proximity they are.

I am curious if that has anything to do with it though.

Thanks for all the info and thoughts from you both. Gives me a lot to think about...
J