I have had my freshwater aquarium going for 16 months now but the only thing that has been a constant struggle is PH, GH and KH

I found that I could not stabilize my PH because my KH was 200ppm , approximately 9-10 drops on the KH test and it should be 100ppm, around 6 drops. Finding out that Magnesium and Calcium in my well water was doing it, I bought an inline filter to take it out. When the water comes out of the filter, it measures under 100ppm of KH, vs the faucet water is 150ppm KH, so I know the filter is doing its job

Now my GH that has been stable all along, is going up to 9 instead of 6 and I can't figure out why? I just added $100.00 worth of plants this week as my others didn't survive my water problems, now I'm trying again and I hate putting those ION pillows in the water, thats what I bought the water filter for, but I don't want to lose the plants again either

How can I now bring down the GH down. I already replace 7 gallons per week of my 55 gallon tank. Its always cystal clear from my Bio-Wheel doing such a great job and I never vacumn as its spotless and all my levels are perfect

Any help will be appreciated

jb