For Sammers and the more experienced growers, I'm wondering if this could be the cause of the sudden collapse?
http://ipm.ucanr.edu/PMG/r107100211.html
http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=6587
Executive Summary: Dry root rot, a fusarium fungus, which teams up with phytophthora and girdles the tree, causing sudden death when exposed to heat stress, wind, or dry air. Symptoms include sudden death of the tree with dry, pale, wilted leaves left on the tree.
The symptoms definitely sound about right.
Q