Re: Yellowing and brown leaf spots
What is happening first, brown/black leaf edges or yellow?
From the bottom photos, there is brown/black leaf edges and no yellowing. This is usually caused by over watering. If you are using a liquid fertilizer every 1 or 2 weeks, then over watering is washing the nutrients away and causing the yellowing as a secondary problem.
May be apply a small amount of slow release fertilizer and dry out the potting soil some. Also, check the pot drain holes are not clogged.
You have to figure it out, but that is what I think I see in the photos. Over watering and fertilizer issues are the biggest problems for container grown bananas.