Newbie seeing first signs of potential trouble
I've had my first true planted tank set up for about two weeks. I have over 3 watts per gallon, pressurized CO2 and tons of plants. No fish yet, and I am just starting my fishless cycle. Plants are all pearling and giving me lots of new growth, but I'm seeing the first symptom of something I think I need to address.
For one of my background plants (don't know the name, but it's the tall one in the center and right of the pic), I'm getting lots of pretty new growth at the top, but some browning and dying down below. I assume this may be an imperfect substrate issue. I have some kind of specialty plant substrate (don't know the brand) under a layer of gravel. I'm guessing these plants are not getting enough nutrients? I'm attaching a picture for diagnosis.
Couple questions: 1) should I pull off the dying parts and replant the healthy parts? 2) is this a sign that I need to add those substrate nutrient sticks? 3) anything else you'd recommend I do to address this?