Bananas require a high potassium fertilizer. I use 6-3-16 from Diamond R Fertilizer - 4100 Glades Cut-Off Road, Fort Pierce, Florida 34981 - 772-464-9300. When I lived in Charlotte, NC I had them ship me the stuff. Comes in 50 lb bags. Great price.
Nothing better. And the bunches are BIG!!!
After moving to PSL I can drive over to them now and save shipping.