Refer-a-Friend

I have a few friends that I started on league, but they never entered in my username(for the old system), and now they have all hit level 30. Is there a way to remedy that? I mean they can all tell you that I got them hooked on it, one even resisted for years against playing it, until I got him to play it a couple times and he was hooked. I can even give you their usernames. Is there a way to attribute those friends to me or am I just hosed?