Brown/black leaves on Ang. distichum - what to do?

[JFeathersmith]

I got this plant on Tuesday, along with several others (auction at orchid society!), and when I was looking over them more closely yesterday, noticed that some of its lowest leaves are clearly dead or dying.

The dark brown/black discoloration (lower left in images) has me very worried that the plant has some sort of bacterial rot. Is there something I can dunk it in or water it with? Or should I just amputate this whole "stem" to prevent it spreading?

The lowest leaf on one of its other stems is yellow, which I'm hoping it just an old leaf dying off, and not a sign of a more systemic problem.

Thanks for any insights!