Pesachim 80: Retroactively Impure - Now What?

What happens if different elements of Bnei Yisrael are impure, and in different kinds of impurity? Those divisions might even be as per the biblical tribes... Would that push the whole tribe to Pesach Sheni? That's difficult, given the unifying role of the Korban Pesach. Also, the case of the korban itself being discovered to have been impure - the meat or the blood, not the person sacrificing - the tzitz of the kohen gadol will ease the way of that offering. It doesn't work for the person making the offering. Plus: Tumat ha-tehom - if one inadvertently comes in contact with the impurity of a dead body, without knowing it until afterwards, when it's too late to avoid... the situation is especially fraught for a nazir, who has essentially taken an oath to not come in contact with a dead body. For this case too, the tzitz will appease for the inadvertent impurity.