וְנַפְשֵׁנוּ קָצָה, בַּלֶּחֶם הַקְּלֹקֵל
and our soul is sick with poor vitality ... Bamidbar 21:5
This phrase tells us that the singular soul (nefesh, not nefashot) of the bodies (not the individual bodies nor the plural souls), of the complainers was "sick with poor vitality." One can suggest then that the complainers were united in a high level of achdut. In fact, their level of achdut was so refined that their nefesh soul was counted as a singular united organism. Having achieved this high level of achdut, the soul required a nourishment that the manna of the desert no longer provided.