I have a customer who has several yaupon hollys in the parking lot of thier business that over the winter lost nearly 100% of their leaf. The plants were not dead and the new growth is starting to show, but I was wondering if anyone has a idea as to what caused this. The shurbs have been in the ground for about 4 years and this is the first time this has happened. The plant name is ilex vomitoria ( "Bordeaux"). The plants are normally evergreen and have not had this problem before. Any clue?