LPL Financial is facing more turnover at the top, this time among its team of investment management professionals.LPL’s chief market strategist, Jeffrey Kleintop, quietly resigned earlier this month to accept a post on the international investment team at The Charles Schwab Corp. Mr. Kleintop had been with LPL for close to eight years.Another top executive on LPL’s investment management team, former senior vice president of research John Guthery, resigned in June to become senior vice president of the product management group at W.P. Carey Inc., a sponsor and investment manager of nontraded real estate trusts. At LPL, where he worked for 19 years, Mr. Guthery also focused on due diligence.