We have (4) 60" box Orange trees at our office that have stayed in their container for a number of years (not planted in ground) but were doing well for 3 years.

Suddenly one of them started declining and rapidly had full crown dieback, within about 2 weeks.

There are no signs of a pest- no rust- no powder- nothing that looks like mildew/ fungus...

I asked maintenance and nothing strange was sprayed back there.

It looked like it was completely dying. Then about a week ago it started vigorously watersprouting from the upper trunk and lower branches.

Really scratching my head on this one.

It's next to 3 other citrus trees in containers which are all fine. No symptoms on other surrounding trees or plants.

Any advice?