SHANGHAI, Oct 13 (Reuters) - China’s rare earth exports in September fell 0.4% from the previous month to their lowest since April, data from the General Administration of Customs showed on Wednesday. Exports of the group of 17 minerals from China, the world’s biggest rare earths producer, were 3,920 tonnes last month. That was down from 3,936.10 tonnes in August but up from September 2020, when overseas demand was still depressed by the coronavirus pandemic. Exports in the first nine months of 2021 were at 35,637 tonnes. (Reporting by Emily Chow Editing by Shri Navaratnam)