Weird Spot on Catt Bulbs

[Corsetière]

I recently was given these two rescue Catts and after cleaning them up a bit I noticed that they both have dark spots on one bulb on each plant. I googled "black spot cattleya" and only got results with black spots on the leaves. Is this some sort of rot or just sun damage? Should I cut off the effected bulb or is there another treatment I should use? The rest of the plant looks fine, no other obvious damage...