If you do use Epsom salts OL. I recommend 2 tablespoons per gallon. Your lawn and roses will love it as well.
"Epsom salts is hydrated magnesium sulfate (about 10 percent magnesium and 13 percent sulfur). Magnesium is critical for seed germination and the production of chlorophyll, fruit, and nuts. Magnesium helps strengthen cell walls and improves plants' uptake of nitrogen, phosphorus, and sulfur."
"The deficiency in the soil may be one reason your tomato leaves yellow between the leaf veins late in the season and fruit production slows down. Epsom salts can keep plants greener and bushier, enhance production of healthier fruit later in the season, and potentially help reduce blossom-end rot. Apply 1 tablespoon of granules around each transplant, or spray a solution of 1 tablespoon Epsom salts per gallon of water at transplanting, first flowering, and fruit set."
Source. 2014 National Gardening Association