Hello, I'm new to the community but googled what you described. Here's what I found so far:
"Massive leaf drop is usually due to a temperature change or fertilizer problem."
"My guess is that it's had too much water. Mine did that at first 'cause I over watered them. I wound up changing my soil to a mixture of 50 o/o soil, 25o/o vermiculite, 25o/o sand. They love it."
I don't know anything about this plant, just what I googled about it.