Tiny black spots on my dendrobiums

[Jassy]

Two of my dendrobium orchids are looking very unhealthy. They have cholorosis and have gone from green to yellowish. Some leaves have progresses to necrosis and fallen off. They have tiny black spots on them that can be scraped off with the pressure. The black spots are everywhere but are more dense in the new growth areas of the plants.

Can anyone help me diagnose what is wrong and how to try and treat it? (I'm afraid it may be too late already however I'm willing to try!)

[kninum]

there are lots of people here to help, but some pictures would really help us help you.
I don't know anything about dens, but i know that the leaves you've desrcibed could be a signal of root rot ...as for the black spots, scale and some other bugs can be spotty, fungus/bacteria is spotty....although i've seen orchids where the spotty seemed to be a normal part of the plant-?-

[ALJ]

I agree that pictures would be useful. Are spots and yellowing primarily on the leaves or the canes also?

[digitalgate]

sound like mold. yak.. dont spray your plant with water. Use a humidity tray.