It's normal for mine... not sure if it's meant to be though
Some older p-bulbs will go like that naturally and some genuses are more likely to go like that. If the roots are in good condition it might be a sign you could water a bit more, but be careful as if the roots are not in good condition then watering more could make them worse.
Personally with that level of wrinkling I wouldn't worry too much. You will probably find they would not 're-plump' anyway even if you changed the conditions. The major thing to watch to tell if your conditions are right is the new growths. If the leaves are crinkled then it's not getting enough water.