150-300 gh! 0-80 kh!

I finally started testing my GH and KH in my 20 Gallon Long.



Before and after water changes my tank parameters over the course of 2 weeks are as follows:

March 23
Ph: 6.8
Ammonia: 0
Nitrite: 0
Nitrate: 20
Chlorine: 0
GH Hardness: 300
KH Alkalinity: 0-40

March 27
Ph: 7.0
Ammonia: 0
Nitrite: 0
Nitrate: 20
Chlorine: 0
GH Hardness: 300
KH Alkalinity: 0-40

March29 Seachem Prime for my 10% Water Top Up

April 3
Ph: 6.8
Ammonia: 0
Nitrite: 0
Nitrate: 20
Chlorine: 0
GH Hardness: 150
KH Alkalinity: 0

April 5 did my usual 2 week 1/3 PWC, also did a complete rescape (new pfs and old Shrimp Stratum) and added in mopani driftwood.

April 6
Ph: 6.8
Ammonia: 0.5
Nitrite: 0
Nitrate: 20
Chlorine: 0
GH Hardness: 150
KH Alkalinity: 80


My tank has survived, no casualties (I'm actually getting Amano Babies, crazy I know)

Is this GH and KH safe or not, im confused on this especially since my tank is doing great.

What should I do?

Note: Im using Tetra strips to get my CHL, GH and KH info. I have an API Kit too which is getting same readings as the Tetra Strips.