It's unusual for 2 fish to just up and die.
Do you have any pictures of them (either alive or dead)?
What symptoms did the loach and bala shark have before dying?
Did you do anything to the tank in the 2 days before they died?
Did you add anything to the tank in the 2 weeks before they died?
How long has the tank been set up for?
What is the ammonia, nitrite, nitrate and pH in numbers?
What sort of filter is on the tank?
How often and how do you clean the filter?
You mention doing water changes 2-3 times a week and adding the normal things.
What things do you add?
How much water do you change?
Do you gravel clean the substrate when you do the water changes?
Do you dechlorinate the new water before adding it to the aquarium?
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Hardness test results can be measured in different scales.
The most common way of measuring hardness in water is ppm (parts per million), which is the same as mg/L (milligrams per litre).
dGH is the German scaling for hardness and is degree General Hardness.
dKH is the same German scaling for degrees Carbonate Hardness. They spell carbonate with a K not a c (Karbonate Hardness).
You can convert dGH to ppm on the "FishForums.net Calculator" at the bottom of the page or on the right side of the page. It's roughly 17.9ppm for 1dGH.
Your test strips are probably reading in ppm. While the numbers you posted below that (GH should be 5-20, KH should be 4-12) are probably German scale dGH and dKH.