I have a banana tree and it is growing very fast. But I am having problems with keeping it to look healthy. Every time the tree starts growing really good, it starts to develop purplish brown spots on the leaves. Eventually where the spots were located it starts to dry up and die in those areas making the tree look unhealthy. Do you have any idea what this could be from? I have it by the window getting good sun light, I water it consistently etc. I have it also in a large pot, fertilizer, mulch etc but it still happens....Any help would be appreciated.

Sorry I dont know what kind I have. It is just big and green with no other charactieristics.