Ops... Maybe it was too cold for it in winter... or too much rain.
It's Phalaenopsis? I don't remember.
The yellowing old leaves is normal. They will die eventually and grow new ones. Brown spots might be from sunburn.
Flower stems also die eventually.
I hope it is not rotting from the inside... then nothing can save it :(
Yes, it's a Phalaenopsis
To spoil your beautiful post with this not nice view:
I think it is not rotten inside ( well, I hope)
The roots look ok, I checked in the pot (the transparent one) and it seems ok. Also, the roots that are outside are ok, just that leaf and some of the buds and flowers in the stems where there are still good flowers are getting brown and black.
I hope it will get better now inside :)
It looks like sunburn to me. Was the sun reaching them there?
I wouldn't worry much then. They like bright light, but no direct sun, especially in Portugal or Spain. The leaf will fall off eventually and those buds too.
Now that you moved it inside all buds might die (blast). Don't worry about it either :) They do that sometimes when they are moved while forming buds. That's how they react when the conditions change.
How many flower spikes it has?
I took today more photos... and probably I will post them these days, I saw that not just that one leaf is affected 😱
and now the change is not making it any favour, too warm inside the living room.
hope the orchid lovers will not cry at the scene hahaha 😂