Question about a Grammatophyllum speciosum

[Mugsie]

I have a 4 bulb plant that seems to be doing well. It has two new spikes coming up, however, one back bulb shows what appears to be a small new pseudo bulb, about one inch tall. Then other day when I checked, the top 1/4" or so of the new pb seemed to be discoloring. Today the little bulb seems to be rotting as it's all discolored.

My question is, have any of you experienced this with this plant? I try to water it well because it's supposed to like lots of water when growing. It resides in a clay pot. The spikes are growing well, but my little PB seems to be gone. Any ideas?