Help! Mysterious rings killing leaves!

[bdublyou]

Had that same thing happen to a very "healthy" appearing dendrobium. I had bought it about a week prior to the onset of syptoms. Whatever it is it spreads very quickly. I threw it out, didn't want to risk infection of my other plants. I recommend you do the same (or send back to orig. grower). My take is, the organism responsible is present already, but then takes over when the plant is stressed (from environment change etc.). It destroys plants very quickly, keep it far, far away from everything else. Spraying fungicide did nothing to slow its progress for me. If you find out anything definitve give us an update--I'd love to know what it is too!