The wrinkled leaves indicate that it isn't getting enough moisture. And since you have it planted in bark with good air circulation it probably isn't from rotting roots, but rather not watering often enough for the pot/medium you are using. You can always use the good old skewer method to see when your medium is drying out, stick that skewer in and leave it for a few minutes and pull it out to see if it is wet. You don't want it to dry out completely before watering, maybe like 60% dry. That's my
Good luck!