Hi, This banana was growing great and then I noticed that the outer leaves stems unwrapped off of the pseudostem down to the base. The next new leaf in the middle looks like it is burnt and is not making much progress. New pups seem to be growing fast and are catching up to the main plant in size. Before this it was growing normally. I did fertilize with a banana fertilizer I bought on Ebay. It was only a tsp per gallon and the other banana plants I have do not exhibit any problems. They all are in the same potting mix to.
The stems also have some black spots on them

Is it fertilizer burn? Should I check the PH, is that important for bananas?

Thanks
Tom