Hey your medium is too dry, you should keep it really moist. Judging by that picture your humidity is around 55% which is too low to keep those cubes hydrated. They way you have it setup will require water every 4-6 hours. Also if you can flip the leaves back over so the plant doesnt have to work as hard to get energy and orient itself. The goal here is to keep the cutting moist and to draw moisture up the stem. By removing all those other rapid rooter cubes, air gets under those cubes and dries them out, try filling the tray until the water hits the bottom of those rapid rooter cubes to allow them to draw up the water that is necessary.