Changing Series chart type in a combo chart changes x-axis values.

Hello, I've attached an excel sheet illustrating the problem I'm having. I want to create a shaded area around the central line by turning the upper and lower bound lines into "area chart" styles, and whiting out the bottom one. However, anytime I try to do this (without tampering with the lines' source data), the "area chart" series get scrunched into a sliver near the y-axis. Help!