Derek Hough, Celine Dion. Getty Images (2) Derek Hough had a bittersweet experience watching Céline Dion’s I Am: Céline Dion documentary after wife Hayley Erbert’s own health struggles. “The documentary was incredibly powerful, showing Celine’s struggles with SPS but also her quirky and fun side,” Hough, 39, wrote via Instagram on Thursday, June…
