Use green plants such as cherry and Viburnum suspensum for hedge work. Let flowering plants grow naturally so you can enjoy the blooms, which occur at the branch tips. I've lost two already. A. Your crotons have lichens , which do not kill the plant. Check the trunk bases for string trimmer damage , which can girdle and kill the plants.
Crotons can live for many years but have thin bark.
A. Pittosporum belongs to a group of plants that prefers drier conditions than they normally receive in the irrigated landscape. Others in this group include citrus, carissa, Texas sage, geranuim, cacti, euphorbia, cassia, queen and areca palms, bird of paradise, royal poinciana, bulnesia, bougainvillea, ligustrum, and most legumes. This is by no means a comprehensive list. Change your watering habits immediately. Pittosporum is subject to root rot.