Brassia pseudobulbs discolored and dented?

[My Green Pets]

I have a problem with my Brassia Spider's Gold.



There are two bulbs, and they are both turning ugly colors and developing big dents and holes.







The opposite side of one bulb looks fine.



Although the bulbs are deteriorating, the two new growths seem to be developing normally.

When squeezed or pushed, the bulbs are firm, even the brown and dented areas. No mushy spots have been found.

I first noticed this a couple of months ago when one half of the pseudobulb's leaf began to yellow. I remember thinking it was odd that only one side was yellowing and not the whole thing. Eventually, the entire leaf detached from the bulb.

I don't know what I'm dealing with, and need some help with this one!