I have 5 mature Wax Myrtles along a fence behind my pool providing wonderful screen, they range from 10-12 feet high. The foliage on one single tree has changed from dark and full to light and thin, on some branches the foliage has died and turned brown. I plan on applying Sick Tree treatment as directed on the bag. What else can I do to save this tree? Will the STT cause damage to plants growing beneath the canopy? I have American Beauty Berry, Inland Sea Oats, Datura and Yucca and Turks Cap all growing under the Myrtles or within close proximity.