We don’t really know anything about your serial device/connection, but generally, and this is true of all the serially connected emon devices, the serial connection must be monogamous, 3 is a crowd and will cause issues, if not immediately, then soon.
The only real alternative is to do it externally in nodered or a custom script, but they involve some coding too, maybe less so with nodered but that’s a lot of overhead and work installing and running just for one task.