Certified GKH Gardening Expert
Are these old leaves, or new leaves? The new leaves will start curled and unfold as it grows. If these are old leaves, then I would suspect overwatering. Make sure that you have plenty of drainage, or have a way to remove all excess water from the container. Make sure to only water once the top two inches of soil are completely dry.
If the soil that you are using is MiracleGro with slow release nitrogen, then this is your problem. I see more problems caused by this soil than anything else.
These two articles will give you an idea of the care of these indoors. There are two main types, so I will include articles for both, since I'm not sure which one that you have: