She also lost the Games record she set in 2014, after India's Tejaswini Sawant set a new record with her 457.9, pipping Ser's previous mark of 449.1.
Semenya said after her double she may even consider expanding her race repertoire to 10,000 meters.
Tracey Neville's side could barely have made life more hard for themselves in the Gold Coast.
A statement later said: "The Cameroon Commonwealth team is sad to announce that eight of the 24 athletes they took to the XXI Commonwealth Games in Gold Coast, Australia are missing from their respective rooms in the Games village".
Five boxers and three weightlifters - representing a third of the Cameroon team - disappeared from the athletes' village at Griffith University on Wednesday, the Cameroon delegation declared.
"The declaration of the competitors ... are both inconsistent and hesitant", Martin told journalists.
The Indian syringe scandal came as five protesters were arrested by police near a shopping mall as an indigenous group continued their Games-long campaign.
In announcing the punishment, the Commonwealth Games Federation had described evidence from Babu and Thodi as "unreliable and evasive", and asked the pair to leave Australia on the next available flight.
There was also to be no hat-trick of gold medals for the 18-year-old Veloso after she finished fourth with a score of 432.3.
Kenyan athletes continue to blow hot and cold at the games, with only a handful of medals in the bag.
England's Alicia Blagg and Katherine Torrance won silver in the 3m synchro diving in hard conditions.
Scotland's Grace Reid won the women's 1m springboard final.
Dallas Stars' WNBA recruit Liz Cambage scored 21 points despite playing less than half the game to lead Australia to a 109-50 win over New Zealand and a gold medal final against England on Saturday.