I read that holly bushes will grow well in full sun but the ones I planted in shade are doing well, but the ones in full sun are dying. The soil is clay, but mixed with sand and a layer of good soil on top with mulch on the surface. I need help. Gary Witham
Why Are My Holly Bushes Dying?
Certified GKH Gardening Expert
Holly does prefer sun but can tolerate and do well in partial shade.
They seem to adapt well to many soil conditions as well.
Inspect the plant carefully for insects or disease.
Clay soil certainly could be an issue with water not draining. This certainly can differ from shrub to shrub.
Are these new plantings? Or established plants?
If they are new plantings and the summer heat and sun can be to much for the plant until the roots take hold.
Here are a few links for you with more information.