I was struggling to keep alk up at the time...it stayed around 8-10 (10 on a good day, 8 was average.) Even after switching salts, I struggled to keep my alk up. But, with the new tank, my alk is solid at 10 (even after a week of no dosing!!!...granted...I did throw away a lot of coral.)
At the initial time of using RSCP, I was changing 10% per week (as I had for the previous 2 years). As the tank kept getting worse, I started changing the water more...and more...and more. I kept changing until I ran out of that bucket and had to use some IO...and magically things improved within an hour or two.
As far as nutrient export, I did a 10% water change weekly (which included blowing out the rocks and cleaning the sand), skimmed wet with the Tunze Nano 9002 skimmer, grew macro-algae, had a RDSB, and used carbon 1 week per month and ran phosphate remover continuously. Nitrates and phosphates have been undetectable for the past 2+ years. Nothing had changed prior to my tank going downhill except changing to a new bucket of RSCP.