Britain's lightweight men's four failed to defend their title as they won bronze behind Australia and Italy at the World Championships in Slovenia.
Chris Bartley, Paul Mattick, Rob Williams and Richard Chambers were dropped at 500m and never recovered.
Britain's women's eight took bronze behind USA and Canada and, in the process, qualified for London 2012.
But in the men's double scull final, Brits Marcus Bateman and Matthew Wells, who won silver in 2010, finished last.
The lightweight men's four arrived in Bled as reigning champions and with high hopes having edged Denmark at the Lucerne regatta in July.
However, the Brits had a poor start and though they recovered to snatch bronze from China at the finish, they never challenged the winners, Australia.
Paul Mattick said: "I'm very proud. This crew's been very good over the past two years.
"We've won 18 out of 22 and we've been in the top three the rest of the time. We'll go on next time."
Richard Chambers added: "You know we're disappointed that we're not world champions again but next year's the big one."
There was better news for the British crew of Alison Knowles, Jo Cook, Jess Eddie, Lindsey Maguire, Natasha Page, Louisa Reeve, Katie Solesbury and Vicky Thornley in the women's eight, as they put the disappointment of finishing fourth at last year's championships behind them.
The Netherlands and Canada were the early leaders as Britain took their time to get going and ran fifth.
But a strong final 500m ensured the crew, coxed by Caroline O'Connor, fought back to take bronze.
Page said: "It's really hard to remember what was happening in the race.
"I recall Caroline calling that we were half a seat off bronze and I remember thinking no way, no way am I going to give up.
"It's my best ever row. I've never won a senior medal before. This is just so special with these guys".
Bateman and Wells, who were world silver medallists in 2010, arrived in Bled with high hopes but they were never in contention, with reigning champions New Zealand edging out 2009 winners Germany in a thrilling photo finish.
Bateman was ill in the night before the race though Wells refused to use that as an excuse and remained confident they could contend in 2012.
"I got woken in the night by Marcus being sick", said Wells. "I only got three hours sleep and he got much less, there was no fuel left in him.
"I went out this morning to train with the spare and we weren't sure if we could race but we made the decision as a team.
"For two fifths of the race, we were really there and even to finish five seconds off the bronze when not totally fit is impressive.
"I think there are seven boats that can win gold next year."
In the non-Olympic classes, Britain's Katherine Copeland, who won the under-23 world title earlier this year, finished fifth in the lightweight women's single scull, while fellow Brit Adam Freeman-Pask finished sixth in the lightweight men's single sculls.
Britain's Alan Campbell was in semi-final action in the men's singles as were Katherine Grainger and Anna Watkins in the women's double scull, with both boats finishing first to reach their respective finals and ensure Olympic qualification.