I hacked it at the bottom of the pseudobulb. Definitely not an old leaf dying. I sprayed it with neem oil (for fungus) even though I know it doesn't look so much like fungus, but I cannot go out to get more chemicals anytime soon. I was thinking of removing from the pot and medium an soaking in peroxide for a bit before potting it back up. Kind of a pain, but I do have peroxide. Would that affect a bacterial infection?