That is probably not caused by a calcium deficiency. Still, with fast growing plants potted in a "soiless" potting mix, it is always a good idea to supply macro nutrients such as calcium and sulfur in soluble form. Often these are not supplied in common fertilizers. I use the fertilizer given in the link below (Note, 5 lb Box) on all of my potted plants. For musa, I use 1 tsp/gal with about every other watering. Here is a link that might be useful: Hydroponic Fertilizer

Sorry if this is a bit late; but bananas absolutely hate to be overwatered. Be sure your soil is drying out before watering, and not staying too wet. It looks like the leaves might be dying off from possibly too much water. Good luck! :D

hmmm... I've go no clue... I'll ask about it over at bananas.org http://www.bananas.org/showthread.php?p=266026#post266026

It looks like outside is not an option? looks like too much water.