First, welcome to the Orchid Board! I agree with the others who have already responded that the problem is most likely dehydration, and it's probably not something that happened quickly. It's probably needed more water for a long time.
I also pot my Phals in large bark, but the wintertime humidity in my home has been in the teens and twenties. As a result, I am watering about every other day for the ones in smaller pots because the bark dries out so quickly. The ones in larger pots can go maybe every three days.
An indoor hygrometer is fairly inexpensive, and might go a long way in helping you understand if your plants are getting enough humidity in the air on most days, and you can adjust your watering accordingly as the seasons change.
It's quite possible that those wrinkled leaves will never totally plump up, but hopefully any new growth will look (and stay) normal with a more frequent watering schedule.
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Cheri
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