Ionocidium "Popcorn" leaf drop

[Myrrth]

Greetings! I purchased two Ionocidium "Popcorn", kept one and gave one to my mom, who's been growing orchids a long time (I've only been growing a few years now). After a week, all the leaves fell off hers with no apparent reason - then the leaves started falling off mine by the two's and threes until there were only a few left. I treated it like an oncidium intergeneric, no direct sun, no extreme temperature, well draining mixture of bark and a little moss. I really liked the plant (note the past tense), and would like to get another one if I find one, but don't want the same thing to happen. Anyone have any idea on what caused this? What I didn't give it? thx