When I bought my home (7 years ago), there was large mature lilac tree, so I am guessing it's at least 15 years old based off when the house was built. For the last 7 years, it has always had dark purple blossoms, but this year they are nearly white with a slight pink/purple tint. All I can figure is maybe it’s the weather we have had this year or maybe the nutrients in my soil have changed. The tree seems healthy as ever and full of leaves and blossoms. Does anyone know what could have caused this sudden change?