Yellow leaf with black dots.

[Synrosion]

I got this very pretty Dendrobiuem at my orchid fair a couple days ago. Like 5 leaves have this weird yellow leaf and big black dots on it. I found it weird but assumed it was dead leaves so I cut it off. But I think it’s happening to more of the leaves. I’ll update you guys if it happens to more but this is the only leaf I didn’t trim.