How are you guys growing this orchid?
What are the day temperatures?
What are the night temperatures?
How humid is it where it is being grown?
How bright is the light?
Is it getting some air circulation?
How often do you water?
Dendrobium finisterrae is one of those in the section Latouria. It is found growing as an epiphyte in the forests of the Finisterre Mountains of New Guinea and Papua New Guinea.
I couldn't find out the monthly averages of the rainfall and temperatures throughout an entire year, but I was able to find a weekly weather forecast of the area.
Here's the link to the weather forecast of that place.
Finisterre Range Mt Gladstone Weather Forecast (500m)
This should give you a basic idea of how to care for this orchid.
I believe the trees this species grows on has moss growing on it, I'm not sure.
I do know that it is humid in that area - (probably somewhere in the high 70's% to mid 80's% relative humidity).
---------- Post added at 04:57 PM ---------- Previous post was at 04:54 PM ----------
Btw, I think those spots are temperature related. Too cool, maybe.
---------- Post added at 05:02 PM ---------- Previous post was at 04:57 PM ----------
A heads up, that weekly forecast are their winter temperatures. They are located just south of the Earth's equator, so the seasons are flipped.
Our summers are their winters.
Their summer temperatures would probably be a bit higher, (somewhere in the mid to high 80's F during the day, perhaps even pushing 90 F). But the night temperatures for the summer would not be lower than 60 F or 70 F.
---------- Post added at 05:29 PM ---------- Previous post was at 05:02 PM ----------
Oh, and I think the pot might be a bit too big. Try downsizing the pot.