MAYBE it's summer doldrums, maybe it's something in the water . . . whatever . . . each week brings talk of another couple curdling. Last week's whisper had Mr. & Mrs. Caroline Kennedy no longer as blissful as, say, Brad and non-wife Angelina. Per best-selling Kennedy author C. David Heymann: "The Schlossbergs always lived separate lives. Ed's not keen on charity functions. He's rarely at her ballets and municipal art things. As for her attending his events, it's debatable what this poet philosopher does, although he's in demand. He works with museum directors programming interactive installations. "They're married 20...