Monday’s announcement by USAA President and CEO Wayne Peacock that he’ll retire next year follows recent departures of at least four other top-ranked officials at the financial-services giant. The news also comes amid a string of tumultuous developments for the San Antonio-based company, which serves military personnel, veterans and their families. Those include the first annual loss in the firm’s history, a major lawsuit settlement, fines from regulators and other high-profile legal disputes.