I think it is not the pH value that is the most important. If you would use phosphoric acid or HCL you have a strong decrease in the pH value but only a minor effect on the micorbial status. Citric acid etc are not the strongest product for an efficient product. In small doses it is used as nutrient for some microbes. there is good knowledge today about the usage of fatty acids against some microbes in water. These acids are specially formic acid in combinations with more expensive acids or medium chained fatty acids. The formic acid is than used to reduce the pH with the lower pH value the usage of the more expensive Acids can be drastic reduced.
With the usage of this kind of products you have in the most cases better results and less problems with wet litter.
Greetings