We live southwest of Phoenix on an irrigated acre. We planted 4 Tipu about 5-6 years ago, All were 24" box. Three are in a straight line about 30 feet apart at the back of the property, the 4th is about 75 yards away, up closer to the house. Over the past 5 days, almost all the leave have turned brown and about half have dropped. This behavior is very much like Texas root rot, but I cannot find any information about whether or not Tipu are susceptible to root rot. Does anyone have any ideas about what could cause this in 4 trees at the same time?