Could be water or sun damage. I'd leave the leaves. They have a lot of green on them so will help the plant. If you want to "pretty it up", trim off the brown parts with a pair of scissors. I'd definitely transplant, gently, to a larger pot filled with good soil (I use County compost so don't know much about musas and purchased soils) and drainage holes. Water well. Enjoy your new addiction...er...addition.
