A couple pics of the bananas in question:

Michael,

Over fertilization is certainly possible, but rarely through 'natural' means. Grass, compost, worm casings and slow release fertilizer won't do it, even when mixed together.

Your plants are still relatively small. They've been adjusting to the changing weather and getting ready to kick into high gear. The leaves are fairly large for a small plant, so transpiration is great, and the bananas can suffer a bit when they get thirsty at this stage.

Once your plants are about 4 ft in height (measured from the base of the plant to the bottom of the highest pseudostem) bananas can take up to a lb of Nitrogen and anywhere from .75 to 1.5 lbs of Potassium per month.

I've piled on the slow release, drowned them in Miracle Gro Blue, and more without issue. As long as you don't fertilize fresh transplants, they should be fine.

As this post is nearly a month old, any update? I'm assuming everything was copacetic?

Mike

They are still about the same as when I first posted with about the same amount of yellowing to them, though both have put on a few more leaves. I hand-water them every morning with water from my rainbarrel and sometimes give them more in the afternoon, especially of late since we have gotten very little rainfall. I may end up getting a soaker hose, attach it to the rainbarrel and open the spigot to a slow trickle, though the rainbarrel itself has gotten fairly low, again due to our lack of rain. El Nino sucks.

Try backing off the watering for awhile. Once, maybe twice a week give them a deep watering. I know it's crazy hot and the rain gods are busy elsewhere, but at that size, the plants aren't THAT thirsty. In pots, maybe, but in the ground, they're fine.

Just like trees, you're trying to encourage more root growth. You've also got to be cautious of root/corm rot. Your plants are just on the edge of explosive growth, but they also need to be able to do things for themselves. Tough love will see you through! lol

Mike

I will do that. And it makes sense as I actually have another that is in a pot and because of its location, I often forget about it while doing my watering, yet it looks better than these two in-ground.

It is possible to burn with enough of anything artificial, or manure that is fresh, but doubtful with what you are using. I have fertilized Bananas with Miracle Grow every 3 days all summer with no bad effects, it was enough to burn the native weeds growing around them, but the Bananas just get getting bigger. I have seen people scoop the blue fertilizer straight into the pots and water it, but I have yet to try that lol, and probably wont as it seems harsh. Tropicals are much different in nutrition requirements than the plants that normally grow where I live. My Brugmansia can be fertilized full strength every couple of days without burn, and sometimes that's the only way I can get them to form buds. Biggest problem I have had with over fertilization with tropicals is not burn, but it can throw the soil chemistry out of wack, and bind up certain things like calcium, magnesium due to antagonism, and can actually cause deficiencies. Anything too acidic, or too alkaline will do this also, making the nutrients unavailable to the plants, even though you are feeding them like crazy. At a ph of 5.5, my bananas start to get some calcium issues. Only thing I have used that will change the color of banana leaves to a light yellow green is epsom salt, and to me it proves foliar feeding does indeed deliver nutrients through the leaves, because the next day after spraying, the leaves always turn a lighter green. Bananas will fold like that when it gets hot, even when watered properly, it reduces the surface area to the sun, and keeps them from losing too much moisture.