sounds like a good set up and a good plan going forward.
my 2 cents.
I dont like jumping to chemicals first. esp as in a new tank. chemipure and purigen can be pretty harsh i know at least on corals. (canary in a mine?) and should be added slowly(you might I dont know). And dont they both do the same thing? po stripping? so theyre double stripping? do you even need it?
I know we gotta do what we gotta do ($$) but test the distilled, you may even need to just switch brands. I had a lot of fish death and failure due to my ro source. And it was a PRO source well recommended etc.
chlorine is an oft used additive fda approved bla bla but it kills bacteria, in the tank and your gut. no bacteria no digestion, no immune system.
heres an interesting discussion, mainly on qt but it opened my eyes on fish health and food sources.
https://www.reef2reef.com/threads/two-methodoligies-to-keep-a-reef-tank.226995/
are you using something like Prime? its a mild bacterial booster slime coat water conditioner? Healthy bacteria and its regulation can work very well for nutrient reduction (see Randy Farley, no GFO... fuge/skimmer instead)
same principal as miracle mud and refugium.
Somtimes we take too much out and don't leave enough in.
Good luck.