We adopted our boys from Pets at Home, and they were estimated at 10 - 12 weeks at the time. They had been out on the floor for a while but no one wanted them, so they got moved to the adoption section so that they (the shop) could put new rabbits out.
It turned out they had ringworm which developed after we had them for a week or so, but luckily the store manager agree that the store would pay for the treatment, so they got the expensive oral solution.
We get the majority of the supplies and toys etc from Pets at Home, and our vets is based within the store so we are in there fairly regularly.
I simply don't believe that some of the rabbits they sell are old enough, they are so tiny.