Phalenopsis full bloom but dehydrated leaves

[silken]

I agree, if it has never been watered, it is just dying of thirst. Even orchids in the wild get frequently rained on. Depending what media you have, watering it once a week to every two weeks would likely work. The skewer method is great for preventing root rot. Just insert a thin bamboo kebab skewer into the center of the media quite far down. Leave it there and then pull it out to check how wet or dry it is before watering. It will tell you when to water. If it is wet, wait. If it is bone dry, you waited a bit to long. Just damp or close to dry is usually about right and then water the plant well. Put the skewer in the same place always so you don't stab multiple roots.

If the roots are not hollow or soft and mushy leave them. Even if they are grey,. They are likely severely dehydrated and may recover.