first image is the bottom of a removed leaf

second image is the top of the same removed leaf

third image is the bottom of an attached leaf

fourth image is the top of the attached leaf

image

other image

last leaf bottom side

last leaf top side

I'm not an expert on orchids but it kind of looks like mesophyll collapse to me. It's caused by exposure to cold air or water. Do you use any kind of fertilizer? The browning could be fertilizer burn. Maybe someone else can give you a definite a confirmation.

Some of the images remind me of when I had mites on one of my orchids. If you could wipe the leaves with a wet paper towel and see if you can see redish looking spots on the paper towel and post whether there is or isn't anything.

Maybe mesophyll collapse... maybe spider mite/broad mites or other mites... Maybe virus... I had many Phals with such leaves and they had been positive for Odotontoglossum Ringspot Virus and Cymbidium Mosaic Virus

Dismissing the brown spots for now.

BUT, the second leaf in the picture is dilapidating at a fast rate (becoming limp and floppy).

All affected leaves in the pictures above are on the same side. However, on the other side, though I don't see any of the initial problems on the leaf, it too is becoming limp... at the crown, this leaf is just below.

Wiped leaves with a damp paper towel, and there is nothing coming away, no red spots. It's clean.

With these three possibilities, what can I do to fix or stop or treat?:
a) mesophyll collapse
b) Odotontoglossum Ringspot Virus
c) Cymbidium Mosaic Virus

Or, is it a goner? :(