Terumos 3:2-3

Terumos 3:2

If either the first or the second terumah (from the case in Mishna 3:1) fell into chulin (non-sanctified food), it does not cause it to become meduma (prohibited to a non-kohein). If the second one fell into different chulin, it does not make it meduma. If both the first and second fell into the same chulin, they jointly render it meduma, based on the volume of the smaller one. (All of these cases are leniencies in matters of rabbinic law based on the doubt as to which one is actually terumah.)

Terumos 3:3

If two partners each took terumah separately, Rabbi Akiva says that both are terumah; the Sages say that only the first is terumah. Rabbi Yosi says that if the first one separated enough, then what the second one did is not terumah; if the first did not separate enough, what the second one did is terumah.