Most likely, the tree was improperly installed. Improper installation with trees is completely different than most plants. This is because the biology of the tree allows it to remain in the ground in a state of decline, sometimes for 15 years or more. The average life of a tree improperly installed is 7 to 10 years. Trees that were planted wrong have major problems with their anatomy and physiology. The root system has major defects, and those defects can easily be misdiagnosed as many other things. A lot of the time, people think that it is a watering issue, when in fact the root system has strangled the tree and restricted the flow of water and nutrients. Trees that have been improperly installed can receive preventative or active treatments. The use of a pneumatic-air device is advised, such as an air spade or air knife. We have included some photos of some improperly planted trees and a video explaining how you can inspect your tree for yourself to see if it was planted correctly. For information on how to plant a new tree, please see the link (how to plant a new tree).
