I'm assuming you want to use the same `PlotRange` for cell (2,2) as for the other cells.

You can change the order: show `Plot` before `ListPlot`. Note that I had `Plot` set the `PlotRange; by default, the first function called by show controls the graphics settings.

 Show[Plot[cumulativeGauss[x, fit2[[1]], fit2[[2]]], {x, 0, 30}, 
 PlotRange -> {{0, 30}, {0, 1}}],
 ListPlot[data2]
 ]

![PlotRange][1]


 [1]: https://i.sstatic.net/og85n.png