I have several new phals in my collection and the new buds on the spikes come out hearty and green, but before they open, they wither and fall off!!! What's wrong? Repotting maybe? Not enough fertilizer? I know it's not overwatering... I keep a very good check on that...
Knowing your growing conditions would help us give you an answer, but I'll mention what I did for the same problem. I added some supplemental light, and believe it or not, increased the watering a bit. Here in Reno, It's hard to believe how fast things can dry out in the winter. Maybe a little higher temps during the day, too. Hope this helps 'till an 'expert' chimes in.
The fact that they are new phals might explain the problem, if you bought them already in bud. Changes in conditions from the store to home frequently cause bud blast.
Otherwise I agree with Tuvoc that it probably something with their environment. How's the humidity? If it's really low it be a reason. Or maybe a draft going over them? Too cold? It could be lots of things!
__________________ Camille
Completely orchid obsessed and loving every minute of it....