Try Gypsum as a topdress if your in soil instead of the carbonates. Egg shells will take months/years to become available. The sulfate in most scenarios will release the calcium and bind to magnesium in your soil creating magnesium sulfate which is leachable and will correct situations of too much mag in your soil. Save the Epsom for foliar so that you can really push higher K levels by having the higher calcium levels in there. Does that make sense?