problem in regard to hot standby

Hi all,
I have encounted the problem with the hot standby, The master node was suddenly powered off,meanwhile,both two standby node had shut down end printed logs as followed:

PG version:9.6.8

2019-01-13 09:35:42.831 CST,,,28904,,5c332ceb.70e8,5,,2019-01-07 18:41:47 CST,,0,LOG,00000,"replication terminated by primary server","End of WAL reached on timeline 3 at 1/D49ADFF0.",,,,,,,"WalReceiverMain,walreceiver.c:456",""
2019-01-13 09:35:42.831 CST,,,28904,,5c332ceb.70e8,6,,2019-01-07 18:41:47 CST,,0,FATAL,XX000,"could not send end-of-streaming message to primary:no COPY in progress",,,,,,,,"libpqrcv_endstreaming,libpqwalreceiver.c:282",""
2019-01-13 09:35:42.876 CST,,,28904,,5c332ceb.70e8,7,,2019-01-07 18:41:47 CST,1/0,0,FATAL,XX000,"invalid memory alloc request size 1701675008",,,,,,,,"palloc_extended,mcxt.c:961",""
2019-01-13 09:35:42.945 CST,,,28771,,5c332ceb.7063,3,,2019-01-07 18:41:47 CST,,0,LOG,00000,"startup process(PID 28883) exited with exit code 1",,,,,,,,"LogChildExit,postmaster.c:3552",""
2019-01-13 09:35:42.945 CST,,,28771,,5c332ceb.7063,4,,2019-01-07 18:41:47 CST,,0,LOG,00000,"terminating any other active server processes",,,,,,,,"HandleChildCrash,postmaster.c:3294",""
2019-01-13 09:35:43.119 CST,,,28771,,5c332ceb.7063,5,,2019-01-07 18:41:47 CST,,0,LOG,00000,"database system is shut down",,,,,,,,"UnlinkLockFiles,miscinit.c:755",""

Can anyone please tell me why standby nodes shut down and what i suppose to do make the cluster back to normal again?

Regards