Honestly bro, I don't even check my pH anymore unless I'm checking for CO2, as long as it's between 6-8 I feel safe, but as far as plants, that's a wide range to grow in, and I'm serious it is a wide wide range.
Just let it ride, maybe in your non-planted you have something hard that's making your water harder, and not sure about your dirt in the planted, there's alot of stuff in dirt to play with not really sure how that fares against the pH level.
The drop in NH4, and rise in NO2 tells me your mid-way through your cycling process. I would honestly let this do it's thing before you go and add crap to the tank. Too many people rush this process, and the best way, the quickest way is to just wait it out.
As for CO2, try the DIY method, there's a whole slew of ways to make it, mix it, diffuse it. It's super easy bro, too easy.
Hope I helped