Miltoniopsis spikes drying up

[seaj]

Here are the spikes that are drying up. Notice the nonexistent pseudobulb they are growing from.


Here is a mature pbulb on the left. The one pictured above is on the right. There are also 3 new pbulbs forming.


Here is a picture from a few weeks back. The 3 spikes that came fully bloomed on the plant are much longer than the two spikes that bloomed between the foliage under my care.


The temps in the house are 65-72 degrees and the plant is in front of an eastern facing window. The humidity in the house is probably on the lower end, and I haven't checked the roots because I didn't want to disturb it while it was blooming. I may have over fertilized it.

Why were the newly bloomed spikes so short?
What could cause the last two spikes to dry up?