This is a Dendrobium. Some of these are naturally deciduous, but they flower on bare plants and before the foliage has regrown. That is not the case here though, and sounds like something is wrong.
We have to see what Dendrobium growers have to say (I only have D kingianum, for the perfume). I will be interested to see what they think of charcoal as a medium.
Sorry I can't help, but others will!