HONG KONG—Shares of China Evergrande Group tumbled on Thursday after the embattled real estate developer did not pay offshore coupons due earlier this week. Evergrande, whose $19 billion in international bonds are in cross-default after missing a deadline to pay coupons earlier this month, had new coupon payments worth $255 million due on Tuesday for its June 2023 and 2025 notes. At least some investors holding the two bonds have not yet received the coupons, according to three sources with knowledge of the matter. Both the payments have a 30-day grace period. Evergrande’s shares ended down 9.1 percent on Thursday, while the benchmark Hang Seng index edged up 0.1 percent. Bloomberg News reported earlier that the due date passed with no sign of payment by the property developer. Evergrande’s Thursday decline wiped out gains from earlier this week, when the market cheered the initial progress made by the firm in …