That would mean that it is too dry and needs more moisture. That can be avoided by using half and half instead of milk, or at least whole version instead of low fat. Berries can add tenderness as well, as well as drizzling maple syrup or honey on top to seep in once done. Do NOT bake it too long either. Instead, bake for the min. amount and check to see if it feels fairly firm when touched gently. If it sinks it needs a few more minutes, or if it is hard you've baked it too long. It is a fine line. When making corn muffins remove from the pan to cool on a rack instead of the pan.