Wrinkled, squishy phal leaves

[sthh]

When the leaves are wrinkled, always check the roots. Do you have healthy roots?
Overwatering can rot the roots, and you will have wrinkled leaves.
Underwatering will shrivel the roots, and you will have wrinkled leaves too.

If you are underwatering, just add a bit more water. Do not overwhelm the phal with lots more watering, as a weakened plant may not respond well to that. Then wait for new roots to appear, and your phal will be fine.