I have planted a total of four Loropetalum's this summer, and three have lost their leaves almost over night and died. I live in zone 8a (upper South Carolina) and we've had an extremely hot, dry summer. I've watered my plants daily to provide the necessary water they need. My yard is sandy; however, I added top soil and peat moss to the area when I initially planted.
Loropetalum’s Planted Keep Losing Leaves and Dying
Certified GKH Gardening Expert
Your shrubs likely just did not do well with the stress of planting in the heat. Watering is the key and with sandy conditions the drainage of moisture may have not allowed the roots to draw up the moisture.
2 to 3 inches of hardwood mulch around the plants can help with moisture retention. Also tamp around the base of the plant to make sure there are not any air pockets around the roots.
Continue to add moisture until the plants are dormant.
Keep in mind that most reputable garden centers will guarantee plants and trees for 1 year.