Things I noticed were that the surrounding soil looks very acid due to all those weeds growing.
So the plant might be showing some acidity issues like calcium deficiency.
I can't see any nitrogen deficiency in the plant you've shown us.
Bananas like neutral pH or slightly acid 5.5 -6.5 pH range rich well drained compost rich soil.
With lots of water and high humidity and not a lot of wind or bright sun.
Sun and wind are ok as long as it has good protection which yours does not have yet because it is planted right out ion the middle of the lawn.
So test your pH and adjust with lime if necessary. Add lots of compost (real compost, not bought in a bag from the big box store) If you don't have real compost, get as many different manures as you can find and mix them all together making sure the whole is nice and moist but not dripping wet. Leave a couple of days to form a spongy texture and for the heat to dissipate, then dig in several handfuls of that in around each tree.
Bananas also like a good amount of blood and bone fertilizer. They are heavy feeders so go heavy on the fertilizer and in particular potassium because the flower and bunch is being formed right now in the base of the trunk. Depending on the variety, it will produce 45-60 leaves then it will flower. But that flower is in need of potassium right now as it forms.
Some varieties have red tingeing along the leaf edges and stem so I would find a better picture of your variety to be sure that isn't what's happening. Also, the sun will change the colouration.
