It’s what I call pleated leaves and is usually caused by a lack of moisture reaching the growing part of the plant. This can be caused by not watering enough or even watering too much.Check the roots gently tip the plant out of it’s pot and examine the roots, if they are white or tan coloured, firm and spread out around the pot, you’ll need to increase your watering frequency. If the roots are brown and mushy trim them off, repot in new media and reduce your watering frequency.