The cynic in me says that this was all started by folks who make a ton of money selling Epsom salt and baking soda at hundreds of percent profit margin. Just speaking generally here, for example, the parent company that owns Aqueon, also owns multiple tropical fish farms... so, seems to me that perhaps there is a potential for a conflict of interest insofar as the advice given by them goes. And quite probably all the folks they sponsor are well aware of the same "Facts" so they spout them from the pulpits of YouTube, and before long, everybody just absolutely KNOWS that if you want to keep African's you gotta run between 9-18 DGH! Then everybody is buying a couple of things:
1. Lots of "salts" and "buffers" - gotta pump them numbers up!
2. Lots of pH tests. You gotta test it a lot to make sure it's in the correct range! Be afraid!
3. Special substrates - aragonite, cichlid sand, you name it.
4. Scrapers! You gotta deal with all them hard water marks
5. replacement pumps and impellers - geez! Hard water, amirite?
Folks want to sell you things.
KH should be kept over a 3 just to prevent fast downward pH movement. This is not as likely to happen in a tank with frequent water changes, as it is usually caused by lots of nitrates causing nitric acid to build up. I'd just bring the KH up to a solid 3 with baking soda and see if you can live with the resulting pH.