brown spot on leaf of Paphiopedilum

[WaterWitchin]

My first thought was same as Ray's. Hard to tell from the picture, but the medium looks either like potting soil, or very broken down.

And as Aliceinwl says... at what temp has it been kept? I have a couple where temp was below 60 at night for a month or more, and the older leaves looked the same.

I'd get it out of the pot and see how much viable root is there. My guess is likely not much. Repot in better media. Can't hurt, since it's on a downhill slope at the moment.