I was going to let Lou's comment stand alone, but... lol
OLike Lou I think two part additives will not result in complete sea salt because they lack some components. I assume that most lack sulfate. It is very easy to check for sulfate:.
But you've not tested any to see?
Even my DIY has an appropriate amount of sulfate when used as directed.
As to other brands, they make claims about their products that are quite similar to yours, and I have no reason to doubt them any more than Tropic Marin.
Examples:
ESV:
http://www.esvco.com/products.html
"In addition to supplying highly concentrated calcium and carbonate alkalinity required for calcification, B-Ionic Calcium Buffer System is also formulated
to provide all other important major, minor, and trace elements in the proper ratios to duplicate the composition of synthetic seawater."
Two Little Fishies C-Balance:
C-Balance from Two Little Fishies is a two-part, calcium and alkalinity maintenance system that adjusts calcium, magnesium, and strontium ions to natural seawater ratios,
and achieves a balanced ionic residual.
Part A ingredients
Calcium Chloride, Magnesium Chloride, Calcium Bromide, Strontium Chloride, Lithium Chloride, Rubidium Chloride, Nickel Chloride, Chromium Chloride, Zinc Chloride, Copper Chloride, Cesium Chloride, Iron Chloride, Manganese Chloride, Cobalt Chloride.
Part B ingredients
Sodium Bicarbonate, Sodium Carbonate, Sodium Sulfate, Potassium Bicarbonate, Sodium Metaborate, Sodium Fluoride, Potassium Iodide, Sodium Selenate, Sodium Vanadate, Sodium Tungstate.