You will have to excuse me for I'm still adjusting to the mindset of NOT considering nutrients in excess a problem in the aquarium. I'm yet to make the leap of faith into EI dosing regime
I was referring to the PPS-Pro formula which has different ratios. It will limit some of the substances at some point if he's dosing a solution. I didn't used PPS-Pro in an EI fashion and I'm out of my league here
The order as I see it is: Light -> CO2 -> Ferts
Increased light will cause CO2 limiting before ferts. This is because plants have stored resources and will use them in case they're not CO2 limited. Ferts will need to be increased at some point as you will see problems with growth once you're fert limited.