I couldn't find any website for the
nutrients you gave a link to, and that's a red flag that they probably aren't a reputable company. At least not with much experience. Probably some guy selling it out of his garage or something similar. But I wouldn't get the master blend nutes either, that's another one that requires Epsom salts.
Here is a list of good Cost Effective Hydroponic Nutrients that I've found so far.
Cost Effective Hydroponic Nutrients
I'm getting ready to go to bed, so I'll go through and reply to your responses to my other questions when I get up.