Phalaenopsis: Sunburn like leaf damage with white spots - Fungus?

[RavenTheJust]

Hello orchid friends!
My father in law recently died and it turned out that he had a beautiful, yet a little bit neglected Phalaenopsis (needed repotting).
Since my wife would not let me have more orchids (it's fine, really - I only have 14!) it went to my mother in law.

She's not really a pro on orchids - I think she never had one re-potted in her life but I thought there is not much that could go wrong and I could re-pot for her and look how it is going from time to time.

Now she went on holidays and the plant ended up in my care. Unfortunately it looks worse than three weeks ago when I last saw it at her place.
The leaves have become wrinkly but I don't fully understand why. There is not too much moisture in the substrate.
It's old, yes, it needs re-potting, that's clear, but I thought I'd wait until the current bloom is over - if it's healthy it should not be pressing, I thought.
I thought I'd spray it to re-hydrate and see how it goes.

However, while spraying it this morning (my wife brought it home yesterday evening) I noticed an odd area on one of the leaves.
It looks a bit like a regular sunburn but I can't make sense of these white spots which have formed.
Sunburn could be, since my mother in law placed it next to a window where it could get noon-sun and I don't know where my father in law kept it. But these white spots look odd. Could it be scale insects? Or a fungus?

The underside of the leaves looks completely fine - I can't make sense of it. But if it's a fungus, I don't want to spray it - I'd cut the leave and hope that it has not yet spread. If it's scale insects, I actually don't know what to do since I never had them so far..

Any help is greatly appreciated.

Best regards

Lukas