Why might fatty acids, amino acids, and nucleic acids increase the hydrogen ion (H) concentration of a solution?
they all have the organic acid (ie. R - COOH / carboxyl) group which would dissociate (somewhat) in solution, increasing the acidity of the solution
These are all weak acids, as such their respective Ka (ie. fraction of molecules that actually dissociate into ions that would increase [H+]) would release an incredibly small quantity of hydrogen ions in relation to the quantity that already exist in solution.
I wouldn't expect a significant change in pH of the solution, there would be a small (but measureable with the right instruments) increase in hydrogen ion concentration as a small fraction of the acids ionize in solution.