Maybe slow down on the fish additions, add no more than 2 every week or other week. Although you might have just got less than healthy fish; since lots are still fine, just leave it alone for now.
Refractometers, from what I've seen, all read increments on the scale, so unless you mean 1.020 opposed to 1.02, I'm not sure what you're reading.
Stability is key, I'd aim for 1.026 and keep it there. Other than that, looks like a good start to a really nice setup.
Right after you read this, go remove the brass immediately. It will leach copper into your tank, screwing you forever. I mean right now!! Brass bad!
