I am sorry for this delayed reply to your gardening question. We are transitioning to a new Q&A system and your question was unfortunately lost in the transition. I have discovered it now and hope this reply is not too late to be of help.
When banana shrub leaves lose their green color the plant may be lacking nitrogen, the first number on the fertilizer bag. It also can be due to poorly drained soil although this generally results in leaves fading all the way to yellow. Finally when new growth resumes in spring the plant may cast older leaves. I'd start with a good dose of a high nitrogen fertilzer such as a 3-1-2 or higher nitrogen ratio lawn fertiler. Apply 1/4 cup in a 5 foot circle around the bush and water it in well.
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