Its normal for some of the lower leaves to die off, in your case its a few leaves from botoom so more than likely too much sun got it, just trim it about an inch or two from the main stem with a clean knife or clean scissors is what I use. I would separate the pups after they are about 10-12" tall so they can be transplanted safely, yours look about the right size to do it now. Take a sharp shovel angled about a 45 deg to mother plant & cut threw the corm and pull the plant out from under mother plant after you have got all the roots cut from around mother plant & pup, don't worry mother plant will recover quickly & will grow little faster without having to feed the pups anymore. Looks like a very healthy Cavendish Banana you get it to flower yet? I would take a pup or two off your hands if you do not want to replant them.

I can email some pictures of separting pups from mother plant if you like email me.

Thank you for your advice, I'm glad to hear all is ok with my banana plant. I would love to see pictures of separating the pups, how do I email you? Should I try to separate the pups before I bring it in for the winter? Thanks for your help.