fish pollution

I have read that in most tanks the fish waste would be enough fertilizer in aquariums without the need of CO2 or plant ferts. But could an overstocked tank with non-life threatening parameters, and weekly water changes start to deteriorate the leaves of the plants? Such as wisteria and java fern and cause it to get holes that look like they were singed off. My first thought was that the plants did not have enough room in the gravel to grow, thus dying off. As for now I put them in betta cups filled with Searchem Flourite soil hoping to stop the deteriorating. I also read that singed black looking holes appearing in plant leaves is normally nitrates posioning, but I always test my water and is usually fine. Can acidic and low alkalinity and hardiness be the problem? I do not like using chemicals to fix the tank, hence I do water changes weekly. Also my java moss won't spread, even though I put it on mopani wood, and the clump in my cherry red shrimp tank just stays brown and doest' grow. It always stumped me that the java moss is considered a weed that overgrows most tanks, but I am not seeing that.

Any suggestions?

15 watts Floraglow in a 20 gallon tank, I believe it is 2 watts per gallon, but I couldn't find the right bulb for my tank. Also even with this light the java moss isn't even thriving :/.

What is 1 WPG? Also I cannot make my own hood, second, my tank is the regular 20 gallon rectangle shaped tank, the only bulb was the 15 flora glow, anything else would not fit.