Mike, Eximo is a synthetic acid. Eximo has helped many supers but it is expensive and does not react with
carbonate in a straight milliequivalent manner like sulfuric acid. Sometimes lowering the pH of irrigation water will help reduce SAR adj but other times not. If RSC is negative it is simple the quantity of sodium by mass action that is sticking to CEC that is the problem. The sodium is not precipitating with carbonates. In this case you are better using calcium sources to replace sodium on exchange sites.
With a water analysis containing Ca, Mg, K, Na, NH4, Cl, SO4, CO3, HCO3, PO4, and NO3 plus EC and pH you can arrive at all important parameters to solve your problem.
Good luck, contact me if you like.
michaelrogers53@msn.com