If your monstera looks healthy but all of the sudden the leaves are curling in, its trying to tell you something! , The first thing I would check is the soil! , Most common cause of curling leaves is Philodendron leaves are practically black! My mom called it a devil plant : r plants 5 Best Plants for Your Bathroom Low Maintenance Plants Tried air layering for the first time on my Philodendron Plowmanii! : r Aroids