I am going to use RO water with H3AD's formula. So I plan to use 1g of Epsom salt per gallon of water I feet the plants. From what I understand, there are different types of Epsom salts. Like chelated and what not. I picked up a huge container of Epsom Salt from the grocery store. Advertised for foot baths and other muscle related soaking applications. When I went to the garden store they basically said Magnesium Sulfate is restricted, and to just pick up store brand Epsom Salt. Is this correct? Will it work the same?