Most of the majors have experienced a significant depreciation in recent years thanks to the Fed's shift from an exceptionally accommodation monetary policy
position. As the Fed started to talk about hikes, other central banks pursued easing efforts leading their currencies to depreciate versus the Dollar. That was an economic prop for those economies. But, through the rate hike countdown, the Yuan never took advantage - much to China's leaders' chagrin. This likely added to the pressure to devalue.