Issue with spotting on leaves spreading!

[NKOrchid]

Hello!

I posted here a while ago describing an issue with my dendrobium. It had some black spots and I was unsure whether or not they were spreading.
A couple of months later now I can say that they're definitely spreading and I'm scared for my orchids lives. The spots have gotten way worse on the dendrobium and they spread so much I cut down two canes. Now it has four canes left with not so many black spots on, but lots of yellow, dark green and even grey-ish spots! I have no clue what this is. Mites? Fungus?
I've come to terms with the fact that the dendrobium probably will die, but the condition has spread to other plants! As soon as I noticed the spotting a few months ago I took it away from the rest of my collection, but that was apparently too late.
I have another dendrobium who has the black spots now and my beloved masdevallia seems to be suffering too! I'm afraid this will spread or already has spread to all of the orchids and it's just a matter of time before they will all suffer like the dendrobium.
Please help! Any suggestions on what's wrong and what to do will be so appreciated. Thanks!

Dendrobium with grey-ish spots:
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Dendrobium with dark green spots:
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Dendrobium with yellow spots:
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The entire plant that seems to be dying:
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My poor masdevallia:
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