Guarianthe aurantiaca with brown strip on leaf

[Sandrilene]

my Cattleya aurantiaca developed this brown strip down one of its leaves in the last week. I was wondering if anyone had any ideas as to whats wrong with it. it is on a shelf there are orchids above and below it and none of them have anything wrong with them. the leaf in question is farther back on the plant then other leaves which have nothing on them. it is just darker so far there is no textural differences besides just being a different color. should i be worried about a disease? i have had this plant since january. In the photo the dark on the green leaves is my shadow (just so you know).

[kmarch]

This is no longer a cattleya it's a guarianthe so Guarianthe aurantiaca.

It looks like some sort of fungal infection, possibly where the leaf stays wet after being watered or getting rained on? I'd 1) treat it with a good fungicide, 2) keep the leaves dry, and 3) increase air circulation around the plant.