Black spot on zns. Roqueburne

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Welcome to the Orchid Board!

I'm sorry nobody answered this before.

Zyginosia very frequently have a lot of spots that can't be diagnosed.

They are heavy water users. More pure water, like rain or reverse osmosis water, may prevent spots. Many people stand them in dishes with a quarter inch of water at all times.

They like higher humidity if possible.

I would try to correct your conditions if they aren't as above, and see whether this helps.

Edit: You can't tell whether it's a virus without testing. This doesn't look like typical virus infection to me, but virus infection can be asymptomatic.

I would try watering a lot more. Stand the pot in a dish of water.

I don't treat with chemicals unless I know what the problem is, and I know the chemical treats the problem successfully.

This could also be bacterial brown spot, since the spots are sunken. Have a look here; scroll down to "Bacterial Brown Spot on Zygopetalum." It suggests treating with a copper bactericide:
Orchid Questions Answers, St. Augustine Orchid Society, 2011