I just transplanted five hydrangeas. The leaves have gone limp. Should I cut the plants back or wait a few more days?
If your summer has been similar to other parts of the east coast, then recent transplanting will present challenges - just not the best time of year and weather conditions for this activity. Your hydrangeas are suffering from transplant shock. Just keep them well watered until fall rains arrive and don't do any cutting back until spring and you can determine accurately what parts have survived and what has died back.
FWIW, if you could plan your transplanting chores for later into fall or early spring when the plant is not in active growth you will have much less risk of transplant shock.