Problem with leaves

[KittyKat]

One of my phalaenopsis has recently had all it's leaves fall off. At the time it was flowering and on a north facing windowsill next to another phalaenopsis which was fine.

It has been a few weeks now and it's now on a south facing window sill, still flowering, still in a clear pot with the roots getting plenty of sunlight but just without the leaves.

It did not look like the leaves had rotted... they just went wrinkly, then fell off.

Any idea as to what's happened to it? Will it grow leaves again?