Andrew, If that were my plant I would remove the leaf. From past experiences with orchids it's best to get rid of the leaf. What you have is usually a bacteria or fungal problem. Spraying the plant with a bactericide, fungicide will help to prevent it from spreading.

Good luck, Joe

So I pruned about 6 leaves off since they all had the same stuff on them. I then put some fungicide on the remaining leaves as you said. I'm keeping my fingers crossed that the plant will be okay.