Oncidium Buds not opening

[Welfkoondo]

Help please - I'm a fairly experienced grower although only 3-5 years w/ Oncidium Intergenerics. Over the last few months my Intergeneric buds have stopped opening. I see several things:
1) Several petals will open but not all,
2) Buds never fully develop or open (pictures attached), or
3) Spikes turn yellow and dry up.

This is even happening with some of my "old reliables" which have never struggled before. One of them had already opened 4-5 spikes successfully then started doing this. I recently had a Paph also do this - bud got very large then wouldn't open and turned brown.

Any ideas?

Thanks!
Welfkoondo