Did you take all four Epsom Salt drinks without any effects? That is amazing! Did you change types of Epsom Salts ? Make sure they are the type for internal consumption.
Drinking the GF/OO drink won't cause the runs. They will cause the liver and gallbladder to dump lots of bile, but you need the Epsom Salts to open the bile ducts to let the stones pass, and to clear the bowels so the liver/gall bladder wastes can pass through quickly.