David Weir and Ellie Simmonds failed to defend titles at the Paralympic Games in Rio but there was gold to celebrate for Stephanie Millward, Matthew Wylie and Libby Clegg.
Defending champion Weir, who also failed to make it into the top three in the 400m, finished fairly strongly but never looked like catching the leading trio.
Thailand's Prawat Wahoram claimed gold in 3:00.62 ahead of Weir's old rival Marcel Hug from Switzerland, with another Thai athlete Saichon Konjen back in third.
Weir won four gold medals at London 2012 and has three more chances to add to his career Paralympic haul of six golds, two silvers and two bronzes - he races in the 800m, 4x400m relay and marathon.
Hopes of a second Rio gold for swimming star Simmonds were also dashed in the women's S6 400m freestyle final, when she had to settle for bronze.
Simmonds qualified in second for the final but had no answer to Ukraine's Yelyzaveta Mereshko, finishing more than seven seconds behind and also being well beaten by China's Lingling Song. Britain's Ellie Robinson came home in fourth place, a further three seconds behind.
"It just wasn't there, I gave everything I had, but it wasn't good enough," Simmonds said. "This will motivate me. I have two events left, I will enjoy them. They will be tough races.
"I don't know what happened there. I didn't have anything in me tonight. It was just one of those days. Last night I won gold and broke the world record. I had a late, late night, but normally I can do that."
Paralympics GB's 70th medal of the week did arrive in wheelchair fencing, where Piers Gilliver claimed silver in the men's individual epee category A.
The 21-year-old from Gloucestershire was beaten 15-13 by Sun Gang of China, who also defeated him at the World Championships earlier this year.
Another silver was secured in the evening swimming session thanks to S8 400m freestyle gold medallist Ollie Hynd, who finished second in the final of the S8 100m backstroke.
Hynd could not live with the powerful Chinese swimmer Cong Zhou, who broke the world record in finishing in 1:02.90, but he was able to get the better of Robert Griswold of the United States in a tough battle for second.
And the very next race saw Paralympics GB secure a 32nd gold medal when Millward produced a Paralympic record swim in winning the S8 women's 100m backstroke.
Millward went into the race as the fastest qualifier and completely bossed the second half of the race, with her winning time of 1:13.02 more than four seconds quicker than runner-up Maddison Elliott of Australia.
It was an emotional victory for the 36-year-old, who had won seven Paralympic medals in previous races but had not managed to convert any of them into gold.
A busy few minutes saw Paralympics GB make it 33 gold medals when Wylie won a thrilling final of the men's S9 50m freestyle.
Wylie just made the touch ahead of Australia's Timothy Disken, with his winning time of 25.95s just four-hundredths quicker than the runner-up and a further hundredth ahead of bronze medallist Takuro Yamada of Japan.
The 34th gold medal arrived back on the athletics track when Libby Clegg added to her victory in the 100m by winning the T11 200m.
Clegg's chances of victory were eased when Brazilian great Terezinha Guilhermina was disqualified for a false start, and she made no mistake alongside guide runner Chris Clarke, winning in a Paralympic record time of 24.51s.