Over watering, is equally as bad on a container tree as under watering. When a medium is over watered, or is constantly wet, the medium has very little, or possibly no air at all in the tree's root zone. In such a condition the tree will react, and show the same symptoms, as if the medium was totally dry. This is because without available oxygen, roots cannot absorb water, no matter how much water is available. In other words, oxygen must be present for roots to function. I don't know what "'potting and container soil" is, in which the tree is planted in, or what it consist of, but it is either being over watered, or is retaining too much water at the expense of air. One last comment, the tree was purchased 3 months ago (12 weeks). In that time due to the type of fertilizer that was once applied, it has never received any nutrition. A container tree should be fertilized at the very least once a month, and possibly more often during the summer. Another option, would be to use a slow release fertilizer like Osmocote Plus. Osmocote Plus contains all the trace minerals, where as just the regular Osmocote does not.