The Olympic champions relinquished their World Series title last weekend, with South Africa winning the Paris title to open up a massive 34 point lead over nearest rivals England, with one round remaining.
Fiji lost to Samoa in pool play before back to back defeats against Scotland and the United States.
Head coach Gareth Baber said they let themselves down.
"We felt we didn't play to the performance standards that we set previously. We wanted to make up for some of that but what was good about Paris was the introduction of four new faces as well,"he said.