The salts in Alk products will slowly raise your salinity. Also, the massive amount of Mag needed to raise up to 1500 will increase it.
On my last system I was dosing well over 100ml/day of 2-part and had to adjust my salinity every 2 weeks.
If I understand correctly, you had your big 3 kinda where you wanted them 2 weeks ago, and didn't test between then and now?
Sounds like your Alk dosing was set a bit too high.
When I set up a doser, I first get the params where I want them, then test for a couple days
without dosing.
With a little math, or use the
online calculator, I then know fairly closely what the tank uses daily.
Then I set the doser and continue to test Alk daily for a week to ensure the doser is set correctly.
During this time I test Ca every other day.
If after a week all is looking correct, I start testing bi-weekly.