I would say you should still do the addenda if it asks if you have ever had an academic warning issue. If you fail to answer yes, when it applies, there could be future C & F issues from my understanding.
@david.busis Could you expand on why adcoms have dinged applicants for sending a third letter? I had planned on sending two academic letters and a work letter, so I'm just curious. Thanks!
@"Lauren L" honestly I don't know why, though I assume it's because they feel you're making them read something unnecessary. What I do know for sure is that it's happened, especially at Harvard.