Phal leaf has pitting, is it some disease?

[sweta]

Hi,

I got an orchid on clearance and didnt notice the pitting on one of the leaves until I got home. The orchid looks healthy, good roots, leaves, 2 spikes with some of the blooms fallen off most likely naturally withered blooms. Could this be due to spider mites? I didnt notice any mites so far on leaves. Could it be some fungal/bacterial/viral disease. I have a small collection of orchids and I'm afraid of transferring any disease or pests to them. Please suggest what would be the best course of action.