So, you post that your tank is 3 years old which is well mature in terms of your bacteria pop and diversity.
Your nitrates are fine at 8-12ppm and phosphate in the .1ppm to .2ppm would be numbers I would expect with that age, and those are fine IMM.
The dose your using is for lowering nitrates and if that’s where your going that’s fine. It does nothing much for phosphate.
I use the Red Sea Recipe Maker for a general guide to a maintenance type dose and for Nopox it says 7.9ml day on 210 gallons.
Cant say it would have any affect to your corals.