If the pbulbs are shriveling it means the plant needs more water. Bulbos like to be pretty wet from what I gather (I only have one and was told to keep it moist basically all the time). It could also indicate a root problem if you're watering it enough but they're still shriveling. Or it could be that those pbulbs are the older ones and are pretty much finishing their duty as nutrient reserves. It's common for the oldest pbulbs to shrivel once there are new ones present.

Best of luck to you!