My opinion (for what it's worth)
More Light:
At 1 WPG you'll have problems with lots of plants. There are some that will grow at that light level, but you need to choose them carefully.
Your Java fern and Val should be OK with low light .
Your Hygrophila will probably need more light (depending on type).
Your Watersprite (Ceratopteris thalictroides) needs higher light.
More Ferts:
Your Amazon swords will certainly benefit from a substrate fert tab in near the roots. Ferts in the water column will also help with the rest of your plants. Yellow leaves could be a sign of a lack of Iron and/or Potassium in the water/substrate.
More CO2:
I think you need to fix the light level and ferts before adding CO2.
But once you have higher light and nutirents, then CO2 is the way to go.
Remember ..... You need to have a BALANCE of Light/Nutrients/CO2.
Too much or too little of one and you'll get problems with your plants or algae.
If you want to successfully grow plants, then I'd say the first place to start making changes in your current setupi s in your lighting levels, swiftly followed by the nutrients and get some more plants in there, especially some more fast growing stem plants.
I'd avoid adding 'Heavy duty ferts' until you've got the lighting sorted out, or you may end up needing a 'Heavy Duty Algae Scraper'
Then you should add CO2, you should just a about get away with a cheap DIY setup on that sized tank (I had 2 x Nutrafin's on a 28 UK Gal with no problems). But a pressurised system is best, but more expensive.
