First question do all the lambs have the same flock number ?  a dealer may have made up a group from various farms .     You have 2 choices the easiest , fatten them and resell in the spring , you can leave the tags  as they are and maybe at the end make a small profit , provided you didn't pay a lot for them .    Yes you can upgrade to double red eid tags ,so long as you can trace them back to holding of birth .   The license you have should have  the sellers holding  number  so that's a start , then hopefully they were sold at auction by the breeder  , the auction mart should be able to help you get this information .