Citric acid is good for use with organic nutrients but really should not be used with chemical based nutrients. HCl will as said introdoce Chorine and that can be helpful or hurtful depending on the amount added. Used not more than every few days in small amounts it would be fine. Daily use or to make large adjustments would likely amonut to using too much chlorine. Chlorine is commonly used for root rot but at very low dosages. Phosphorc acids or nitric acid are preferred as other than the H+ all they add is a usable fertilizer salt. Nitrogen. Sulfuric acid is another choice as long as not used contiously as it will eventually mean an excess of sulfur which cause the formation of calcium sulfate (gypsum, like in wall board).
Organic acids, citric and acetic (vinegar), should really only be used with organic nutrients.
Klean-Strip is usually in the paint section with the thinners etc, however it is also used to clean/etch concrete.