SEOUL, South Korea—Three members of the K-pop superstar group BTS have been infected with the coronavirus after returning from abroad, their management agency said. RM and Jin were diagnosed with COVID-19 on Saturday evening, the Big Hit Music agency said in a statement. It earlier said another member, Suga, tested positive for the virus on Friday. All three had taken two doses of a COVID-19 vaccine in August, the agency said. The BTS is a seven-member boyband. The four other members are J-Hope, Jungkook, V, and Jimin. According to the agency, RM has exhibited no particular symptoms while Jin is showing mild symptoms including light fever and is undergoing self-treatment at home. The agency said Friday that Suga wasn’t exhibiting symptoms and was administering self-care at home in accordance with the guidelines of the health authorities. RM had tested negative after returning from the United States earlier this month following …