I read at Steve Hampton's website ( Aquarium Plants | My views, Steve Hampton, on how to succeed with aquarium plants ) that :

"Calcium can be added via Calcium Carbonate, Calcium Sulfate, or Calcium Chloride. Magnesium is easy to add with Epsom Salts which is Magnesium Sulfate. Aim for a 4 to 1 ratio and a 5-10ppm minimum for Magnesium."

So for my 600L tank, I added about 9 tsp of Epsom Salt to get 7ppm Mg. And to get a a ratio of 4 to 1 with Ca, I added 20 tsp of Calcium Sulphate; which gave me 28ppm Ca.

The fish looks okay (for now). This has been going on for about 3 days so the cupped leaves of my H.Difformis are yet to respond. But am wondering are all these within a safe and recommended limit? Please advise.