Shot Bloks aren't really an electrolyte supplement. They do have some in there, but mainly they are a fuel/energy source. An easier to digest version of the bars you were eating.

IMO, the easiest way to get the proper electrolytes is to mix a powder into one or both of your waterbottles. Personally I like Camelbak's Elixer and Powerbar's electrolyte powder, but there are a ton out there... try a bunch and see what works for you.