Blast the CO2 until the plants are sticking out the top of the tank. It should look like a glass of 7up you just poured because the plants are pearling so much.
I think the theory behind EI was that it required NO testing. Just change the water. Your plants are still small and the bioload is changing every few days.

I think it's pointless to be testing things although I have been there and you want everything to work today. It takes some time. When the plants really thrive, they just nuke the algea.