I could not see the datasets, but I suggest that you make two changes in your function:
(a) Change ListPlot to ListLinePLot;
(b1) To fill the area between the curves and the horizontal axis, add the following option to ListLinePLot:
Filling -> Axis
(b2) To fill the area between the two curves, add the following option to ListLinePLot:
Filling -> {1 -> {2}}