Help! My Vanda orchid is dying.

[Stanman]

Hi there, I’m new to this forum. I live in the U.K. I’ll be honest, I’ve got experience with orchids but really only Phalaenopsis. I got my first Vanda earlier in the month, brought it home and hung it up. It had a couple of tiny black spots on the underside of it’s leaves but all the Vandas I’d seen at the florists had them so I assumed that wasn’t anything to be concerned about. I wasn’t watering it all that much (about twice a week) and it wasn’t getting much light as it was in the far corner of the room. It started losing leaves like crazy! Serious leaf drop. I haven’t changed my watering routine too much; I have given it more light but both flower spikes rotted and were sticky and I haven’t been able to stop the leaf drop. The roots look absolutely fine however. What am I doing wrong? Could it be overproducing sap and rotting away as a result? I’d love some help. Even if it’s too late for this one, maybe I can prevent losing any other Vandas.