First off, I've had trouble with that brand Phal mix, too fine and the roots don't breathe well enough. I went to coarse bark mixed with some sphagnum moss. If you are lucky, your phals were underwatered and not overwatered into root rot. Changing the media when the roots are not actively growing will cause some trouble, but not, I think, as bad as leaving them in tightly packed moss. I have learned here that new roots grow according to the conditions at the time. If you change the conditions, the old roots can't compensate and tend to slowly die off. The new roots will do well, but the adjustment period is tricky. It's still better than the old roots rotting out fast.
Evaluate the roots - are they sound but dry, or are they mushy and dead? If the roots are good, then give the plant a good soak, let it drain out well and soak it when it dries again. Keep the humidity up so its less stressed too, maybe over a damp pebble tray (but keep the plant's roots out of water). If the roots are mostly dead, cut off the dead roots, let the plant dry out, then keep the humidity up, watch for any sort of rot of the plant, keep the stress down and give it time. Once they are re-potted I still water them as they dry out, but I am careful to be sure they are dry all the way through before I water. Keep the new pot about the size of the root mass, so that the roots are throughout the pot. You want the media to dry evenly, not just around the edges.
I hope this is helpful!