The top half of my bathroom walls are wallpaper. Some of the butt joints have pulled apart (1/32 to 1/16 inch). Also, some on the corners are butted instead of overlapped. Where the corners are butted, they are also pulled apart. The wallpaper is yellow and white vertical stripes. The dark gaps are very unsightly. If I could fill those gaps with some white material, the wall paper would look good. Any ideas how?