For the first two years, my tree gave plenty of sweet, juicy fruits. Now (the past year and 1/2), there is no fruit and there is this odd 'tufty' growth everywhere where there are supposed to be new leaves and blossoms. One nursery said gall. The Pima County co-op extension said it is underwatered. Hope you can solve the mystery.
Odd Growth on Calamansi Citrus Tree
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I doubt that this would be caused by underwatering. Usually, wilting then leaf drop is the first sign of underwatering. I am not framiliar with gall on citrus, however gall usually appears on woody branches and trunks. Gall is usually not widespread over an entire plant.
The description of "fluffy" isn't quite enough to make a decent guess as to the real problem. If it is gray or black and looks like mold, it's probably sooty mold. this article will help: https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm