Q.Why Is My Two Year Old Hydrangea Stunted In Growth With Crisping Leaves. The Leaves Are Small And Eventually Falling Off. It Was P
lanted on a north facing wall. I have a second hydrangea about 15 feet from this one and on the same wall. Planted at the same time, this one is leaps and bounds above it.

Certified GKH Gardening Expert
Likely, this one has a disease that the other is resistant to. Disease resistance can be luck of the draw, but to give it the best chance, a fungicide may be necessary.
This article will help:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
Make sure that the shrubs do not receive too much water. The soil needs to dry out, thoroughly, down to 2 inches or more before watering. Many times, rain water is more than enough without extra watering.
Here is an article to help you with Hydrangea care: