phal bud drop (without blast)

[seamonkey]

I recently bought a lovely mini phal with five open blooms and four unopened but pretty big buds.

Yesterday the daytime temp reached 83 for the first time this year, and the nighttime temp was 75. RH is 55%. Diffuse west exposure light. I had watered the plant the day before, no fertilizer, lukewarm water.

When I woke up this morning all four buds had dropped! The buds were perfectly plump-looking- the weakness seems to have been in the stem.

I have many phals and have never seen this happen before. I mean I've seen bud blast, but never perfectly healthy buds just spontaneously dropping. On inspection, the plant is very healthy with lots of green roots, nice firm leaves and no critters- there wouldn't be much point in posting a pic.

Anyone had this happen to them?