Hammocked Banana

You know how wet your pots are better than me, but it sounds like you either aren't feeding them enough OR you aren't giving them enough water to take up the nutes they need. I find that in the heat of summer, its nearly impossible to over water bananas in pots. I recently had family and friends watering my plants during the week while I was away in the city for work. With the instruction of watering my large potted bananas 10L every other day, they showed sign of underwatering and K deficiency.