Dropdown Menu in Line Chart and Y axis scale

[katknight32]

I have a line chart that contains a drop down list so each time an item is selected the item automatically updates. On all but two of the selections, the scale is proportional to the data. But on those two, the scale begins at 0. If I change the min and max it changes it for all the regions, which I do not want to do. Why are just these regions doing this and not all and how do I change it to scale properly?
On another note, is there a way to have more than one item selected in the drop down menu so it will display the two line graphs over each other for comparison purposes?
I have attached some sample data. Any questions, suggestions would be greatly appreciated.

Thanks,

Katie