When I purchase my Phal. 'Soft Cloud' yesterday, I noticed what appeared to be a slightly browner area on one of the lower leaves. I took a quick look at the underside of the leaf, and didn't see anything going on other then this brownishness.
This afternoon when I check them over, I saw that the it look much larger on the upper surface of the leaf, and it's gone very bad looking on the lower surface.
Give the speed at which this has developed, I think she's got some kind of disease, probably aggravated by the sudden change in environment. I don't see any signs of problems on the rest of the plant anywhere, so I'll cut out the damage portion of the leaf with some sterilize scissors, and give it a good dusting of cinnamon, and hope for the best.