Why does the Minchah of a Sotah comprise coarse barley flour, unlike all Menachos that comprised fine wheat flour?
Rashi, Ramban #1 and Targum Yonasan: Since she behaved like an animal, her Korban consists of animal food.
Ramban #2: Refer to 5:15:2:2.
Ramban #3: Barley
Why was no oil or Levonah (frankincense) added to the Korban?
Rashi, Ramban #1 (citing Tanchuma) and Targum Yonasan: Her Korban is brought unadorned
Why is Minchas Kena'os written in the plural?
Rashi and Ramban #1 (citing the Sifra): Because she has aroused the jealousy of two 'masters', Hashem 1 and her husband.
Ramban #2: "Ki Minchas Kena'os Hi" is the reason that the husband brings the Korban on his wife's behalf
And why is the Minchas Sotah not listed together with the other Menachos in Vayikra?
Ramban #1 (on Pasuk 6): Because it is a Minchas Kena'os, and does not come to atone like the other Menachos.
Ramban #2 (Ibid): Because it is part of the Parshah of Sotah, which the Torah presents here, in order to preserve the sanctity of the camp after having described its detailed Yichus, by determining the Mamzerim 1 via the Din of Sotah.
Ramban: Who are not the children of their mother's husbands