Supplies slim, morale once so heavily inside them
They didn’t have many supplies left from their long journey. Additionally, resources and supplies in the New World were scarce and had to be competed for with the Native Americans.
Also, the meaning behind the full line is their supplies they had brought with them were scare, their once optimistic attitude was waning and both of these things were running out (when added with the line below “now steadily declining”).
To help improve the meaning of these lyrics, visit “Unforgivable Youth” by Lupe Fiasco (Ft. Jason Evigian) Lyrics and leave a comment on the lyrics box