Phalaenopsis flowers failing to open completely

[Ioana]

I grow under lights and on windowsill in winter, outside in summer (in Michigan). Most of my phalaenopsis are quite happy, growing vigorously and spiking/blooming well, but a few plants have flowers that don't open completely (they look like the licastenoid ones, but aren't supposed to be).

First had the problem last year, all in new plants. Thought it might have been too dry, so this year have a humidifier, the room is kept ~ 60% humidity. Didn't help: same plants have the same problem.

No other plants affected (although I do have one other Phal that dropped several buds, also did that last year). No visible bugs on the affected plants.

Temperatures ~ 75F or so during the day, drop to about 65F at night.

Any thoughts?