Glad you found some answers. I may have a bit of old school approach but fish are usually happier in a stable environment, the less you change things the better. I was never a fan of using additives until they’re needed. Purigen in the filter, some Melafix / Pimafix if things went downhill. The water will age if you make small water changes. With large water changes you flush out the beneficial bacteria and while you still have them in your filter, they will need time to repopulate in new water. Shrimps are great cleaners if you don’t mind them and if your fish can tolerate them, they will need hard water and some minerals added every now and then to help with molting.