Probably just genetics. There are several species phals that have mottled leaves. schilleriana & stuartiana are the first that come to my mind, there are others. If you’re suspecting virus and want to be sure it’s safe, you could do a virus test.

Thank you Sheila. I was hoping that all it would be. She only has this one and the flowers were fine, so I don’t think there’s real concern but I was very curious since it was nothing I’ve seen before. Appreciate it!

I don’t like the way they look. Maybe nothing but the way the leaves are curling and the spots not being on the new leaf makes me think there’s a problem.

I’m thinking spider mites or maybe cold damage. There are also Phalaenopsis mites which are similar to spider mites, they are known to attack older leaves and leave new growth alone. If it is cold damage, it could have happened before the new leaf started growing which is why it’s not affected.

I would check with the owner a get some history. Maybe it was outdoors and it got too cold or maybe they have other plants with similar markings