Looks like its rotting all right. The center one looks like a goner. When you cut the tops off, cut until you find green tissue all the way to the center of the pieces. No brown! Let the pieces air dry for a week or so then place them, cut side to the soil, in new potting soil. Press down with your fingers so the cut sides are making good contact with the soil and then wait. Water sparingly until it roots. Then water sparingly so you don't need to do this too often.