it's 90 with a/c?
I suspect in your location it's also humid - tho if indoors with a/c and fans, may be drier ...
While summer this year on the west coast has been cool - normally temps will be mid 80s - mid 90s, with periods of higher temps - tho where I live the temp does drop significantly at night. So while I haven't had issue with heat affecting spikes, it's possible the cooler temps at night may be why ...
Is your plant maybe in a draft - is the a/c blowing on it?
During typical summers, I do water Oncidium alliance pretty often. Tho it's also quite dry here during typical summers ...
Dang - I feel for you
I hope you get another spike soon!