What is wrong with this Phalaenopsis leaf?

[Shadeflower]

all valid possible reasons so I will just add that it could just be past stress signs. Or past sundamage, did this orchid always have this damage or did it develop recently?
Damage like this is permanent. It will get covered by the next leaf and be less noticeable but thats one annoying thing about phals, if they get nibbled on by spider mites the damage stays for years.