2D Line Strokes Turn Thin; Don't Know how to Change Them Back

While trying to make a 2D animation in blender 2.8, I have come across an issue that I’m not sure how to change. I am very new to the program, so I don’t know how it can be fixed.

I had been using the default “Draw Ink” tool to make my lines. One time I opened the project and every single stroke I made turned thin- along with the lines on every previous frame.

This is what the lines are supposed to look like.

This is how they actually appear; only the onion layers have what I drew.

I haven’t been using any modifiers and all blender settings have been reset to the factory settings. Nothing seems off about the original brush as well. Is there any way to change the lines back to the way they were before?