Plant food

I've had my tank running for about three months now and fish in it for 6 weeks. I'm dosing seachem flourish and flourish potassium and also dinosaur spit on a daily basis as per the various bottles recommended levels. I also run co2 during lights on, but as I'm running a sump I get a lot of wastage gassed off no doubt so the tester never goes yellow.

I checked all my parameters today and I have,
Ph 6.8
Nitrite 0
Nitrate 0
Ammonia 0

My filtration is heavy so I was expecting to have all levels at 0.

Should I add the seachem nitrogen to the dosing mix to assist with plant growth or leave it alone?

Thoughts appreciated.