The old leaves on my Brassia and Catasetum are discoloured. I know they yellow and drop leaves naturally, but the leaves aren't exactly yellowing so I don't think its that. The new leaves are fine. Is it some kind of mineral imbalance? Maybe too much light? These are the only two orchids I have that are like this, and coincidentally they also get fed the most and receive the most light.
Edit: Weird, the photos don't show. I thought imgur works on here? I'll just post the link I guess
discoloured leaves - Album on Imgur