That's happened to all of us. Once the top shows signs of heat damage that particular branch will stunt.
You are still early enough in flowering to top her right now. That will redirect the growth hormones to other
parts of the plant where they can be properly utilized. Or, if you feel particularly lucky -- remove the top
right above the next set of growing points. Then trim the bottom leaves off and split the end with a sharp
knife. Put the "clone" in a jar of water and wait for roots.
Good luck, BigSteve.