Vanda leaves never open

[Cewal]

I have a young, blooming-size vanda (though it has not bloomed yet). It is in a wooden vanda basket with no planting medium. The leaves never open on this plant. They appear to be healthy - no pests or fungus, and I fertilize weekly (weakly) or every other week, and mist the roots daily. I also use a plant probiotic monthly. Any ideas on why the leaves don't open? Thanks.