I use it every year as a soil additive when planting the tomatoes and peppers. Soil here is quite sandy so I add about 4 tablespoons to the bottom of each hole and thoroughly mix it with the soil before setting the plants. Never had any negative issues related to using it and never had blossom end rot either, so it's become part of my routine here whether my soil needs it or not.
A update. We did the Epson salt thing, and the deep green color it produced on the house plants, roses and vegetable garden is very noticeable, I would suggest you try using it, I mixed a 1to1 ratio of es and generic plant food of 20,20,20. Applied 1 table spoon to each plant.