Originally Posted by Gabe15

What fertilizer are you using?

I think your problem is too much fertilizer, a small containerized plant like that indoors needs hardly any nutrients, and they very easily build up in the soil and can cause issues just like you are seeing. Also, most tap water has substantial amounts of dissolved minerals which also contribute to this problem.

I would recommend to stop fertilizing, put the pot into your sink or bathtub and water it until water drains out of the pot, do this a few times. There is also no reason you can't repot into a larger pot if your temps in the house are normally above 65 or so, you will see a lot of healthy new growth. When repotting you can mix in a small amount (1-2 tablespoons depending on type) of slow release fertilizer or about 1/3 compost and that should be fine for a while. I normally only fertilize indoor bananas something like every 6-8 months. If they are in a greenhouse or otherwise growing very fast, I would still only do every 3-4 months.