You can use that in anything. It's just magnesium sulfate/epsom salts mixed with water, put in a bottle with a fancy label and cool sounding name, marketed to individuals that don't know anything about plant nutrition.
If you want to add magnesium sulfate to your regimen then just go down to Walgreens, pay less than $5 for a bag of epsom salts, and make gallons of that overpriced nonsense targeted towards cannabis growers.