Be real careful adding epsom salts to the fert solution. It's harder to screw up as a foliar feed.
I'd do the base nutes and water first, then adjust the pH of that, and THEN add molasses. It's a sugar, rather an an ionic substance, so it will affect the pH minimally. If you like, you can alternate feedings between ferts+water and molasses+water. Another approach is to use a carb supplement that is designed for cannabis, and take the guesswork out- but really, just the tablespoon per gallon of molasses that is ALL you need will not mess up your pH.