[saddletramp]

Oh, your water is softened!! Problem discovered. Your softened water is the problem, most likely.
Check your tap water drawn from a source which bypasses the softener. Also, it is best not to be drinking softened water, by the way.
Once you have tested your local water, post it on this thread to get an opinion should you need one.
If you know enough, start your tank over with tap water, non-softened, and you should be OK.
It would help, if you stated where you live. It would help,others know what your local water might be like.
Bill

 

[saddletramp]

Also, a high KH with softened water seems most unusual. There may be other things causing problems.
If your tap water is useable, use it. Try a few plants in plastic flower pots in your bare tank. Set the temperature and lighting properly.
Test the water every other day for a week to see if any changes occur. If you wish and the water parameters permit, use your CO2.
After a month or so of good plant growth, put in a proper substrate and plant your tank.
Test any rock you are unsure of by placing them in some RO water for a week and then test the water for anything unusual in the way of water chemisty.
This is just one idea for you.
But, in the future, test anything you are unsure of before placing it in the tank .
Bill

Yes, you can get an RO unit. Then mix some of your water with the RO. It all depends on the water you start with.
Then, you can make a water change every so often.
Please post results from an unsoftened local water source so people can see it on the thread.