Brassia Rex issue

[Pilot]

Hi All-- this brassia rex has a leaf that looks terrible. Its only one-- the oldest, I believe. Ventilation is good and humidity is not too high. I've sprayed for possible spider mites but never saw any on it (or at least their webs, I didn't see).

Any guess of what this is? I'm not willing to take any chances.

[Izzie]

I'd cut it off and be done with it. Then spray the plant with brown listerine or some other antifungal/bacterial. After fighting stuff like this, I've gotten in the habit of just cutting it off when it gets this bad, so I can pay more attention to the rest of the plant.
Here's hoping it doesn't spread!

[Izzie]

Btw, that's a beautiful (wedding?) band.