Preview and TextEdit Don't Quit When I Close Them

Until recently, apps like Preview, TextEdit, and QuickTime Player would quit when I close all of their windows and direct away from them. For example, if I open an image, close the window, and then clicked on a webpage so that at the top of my screen, it said, "Safari" and no longer said "Preview," Preview would quit itself. Now, none of those app do so anymore, and I have to manually quit them. How do I get that feature back?