Daniel Hymanson’s debut feature is a delicately noticed portrait of extensive-married Chicago artists as they confront their twilight years. The couple at the middle of Daniel Hymanson’s documentary “So Late So Soon” normally look at by themselves to a mouse and an alligator. The characterization feels apt for Jackie and Don Seiden, two ageing artists who’ve occupied a multicolored Victorian residence in Chicago for many years. Jackie scurries all over, dancing, dusting, and decorating their dwelling with identified objects from Furbies to classic suitcases — all in pastel hues of pink, purple, blue, or yellow. Don, in the meantime, sits in his chair as he reads and sketches, like an…