rugged leaf pattern on Paph Leuchochilum

[Kanemix3]

Hello, this is my first time posting here as a years long lurker. I dont have many paph but my collection have been increase each year so I think I might as well sharing here starting now.
Sorry I have to begin my first post with a bad news but can anyone help me identify the problem on my paph leaves?

It came in with very poor root system last year but now it has managed to bounce back until I noticed the rugged pattern on the leaves.

I checked for mites with a jeweler loupe and didn's see any sign of them. Then I thought it could be my lack of fertilizer because I mostly water with RO year round.
The orchid is still going fine whilst making 2 new pups and a new leaf. I dont think it is dying but, I can't get pass with the leaf deformity.
I would be grateful with any help, thank you very much.

this paph grown in the green house outdoor in high humidty all spring and summer long then go back in the house winter with lower humidity.
Medium is mostly inorganic, broken leca, small barks and perlite.
Fert once every month.

 

[Ozpaph]

maybe just older leaves that have supported the new growth when the roots werent good?

 

[Djthomp28]

I have always thought of this as a watering or humidity issue. It shows up on my brachys when I have been inconsistent with watering. I am curious about what others think.

 

[DrLeslieEe]

It could be either water left on leaves overnight (secondary bacteria or fungus attack) or water/nutritional deficiency. Happens in my leucochilum collection.