Phal flowering issues

[karlos879]

I'm still very new to all this but I have been lucky enough to get hold of some cheap flasks and grow a number of phals this past year or so to add to my mature plants.

The problem I am having is this:

I am getting a good number of flower spikes on the mature plants, with good high stems, but most of the time (in the last 2 months or so) the buds appear, grow a little, then shrivel up and fall off. The plant then tries again to flower and the same thing happens.
They are split between a greenhouse and the house, and the same thing has happened in both locations.
What am I doing wrong here? Not enough humidity? Too hot?

Any help would be greatly appreciated.
Thanks,
Karl.