Hard Cane Dendrobium brown leaf spotting and yellowing

[ViolinFin]

Got a new antelope hard cane dendrobium about a month ago. It's a den johannis x touch of gold hybrid.

Been getting these spots on the leaves and I have only been watering the substrate, not the ever wetting the leaves. The leaves affected appear to only be the bottom leaves. The two leaves I had that originally had it fell off.

I am also growing indoors on a south window on a 12th floor apartment in Seattle. It gets a lot of light, maybe too much at times? I also try to keep it near a humidifier.

What is this and how can I rectify it?

[ViolinFin]

Here is the whole plant. It's growing a new cane from the base.

[estación seca]

Welcome to the Orchid Board.

What are your temperatures? This is a warm to hot growing plant.

[ViolinFin]

Thanks! Been a long time stalker of the forum

Temperatures during the day currently are around 75-80F degrees because of how warm the sun coming through the window is. I just plopped a hydrometer next to it and the humidity was damn low (25%) unless I had my humidifier on near it. Now it is at 40-50% depending on time of day.

Temperatures at night are probably no lower than 63F and are closer to 68-70F as my guess.

[estación seca]

Plants become more susceptible to fungi when they're outside their normal temperature range. I think it would be a lot happier if you could give it warmer nights. 63 F / 17C is lower than it wants unless the next day would be a lot warmer.

As for the spots - draw a circle around them with a fine marker. If they don't spread, don't worry too much.

Dens. will get very spotty leaves when they're dropping naturally, but that also happens when they drop naturally but prematurely. Dens. in the antelope and phal group drop leaves prematurely when they're too cool or not watered enough. I think yours looks watered enough.

[ViolinFin]

I'll monitor the temperatures tonight to see how cool it gets. The apartment is pretty well insulated with no drafts, so at least that's not of concern.
I've been watering it when it's approaching dryness to drying. Is that not enough or a fine approach?

As for the spots not spreading, do you mean the spots expanding in diameter or multiplying on different areas of the leaf?
Thanks!

---------- Post added at 11:27 PM ---------- Previous post was at 10:35 PM ----------

Is it possibly a virus? Every reddit plant wizard from past posts seems to think its Cymbidium Mosaic Virus or something terrible.
If it were CMV, wouldn't all leaves be affected at once?

[estación seca]

You can't identify viral infection without testing. But the spots on your plant don't look to me like the online photos I see of cymbidium mosaic virus in Dendrobiums. The spots look like fungal infections, possibly after an insect bit the leaf. They also look like cool temperature damage.

I meant spots expanding in diameter.

[ViolinFin]

My climate conditions as well as visual update of the plant as of 9:30PM.

Looks like a pretty stark difference since yesterday. The areas around the brown spots are like a caldera on a volcano. Never seen an orchid spot have a raised pit, but perhaps thats just due to the leaf thickness. I ordered Physan 20 in hopes that it would halt any progression of infection

[estación seca]

Those look to me like leaves aging and falling off normally. It can be frightening. That's how this kind of Den. does things.

I would let it get close to dry between waterings, but not completely dry, because of making the new growth.

[ViolinFin]

Any idea why there is that yellowing streak on the second to bottom leaf? Is that problematic? Or is that also due to aging?