the eid and second tag MUST have the same identifying details, the only time you should be adding tags is if the originals are lost and you are using red replacements or you have complete details of the old eid tags and replace with a new set of tags and note the change in your records.
I just had a thought! some store lambs under 9 months old can be moved on a non eid slaughter tag so it may be that so long as your lambs are slaughtered before 9 months then they may be correct. but I would suspect that you would not be allowed to upgrade later and that you must not make any changes to the tagging
when I started writing this I was confident in what I was saying... now I'm not so sure