Thanks, that advice helps! Do you have any specific recommendations based on the pictures I posted as to why my plants aren't doing well with NPK, Flourish, and glutural? I feel like it's lighting at this point but any more light leads to bad algae issues for me. I might get a BGA product but I feel like that's a band aid for an underlying problem.
The most successful BGA treatment I have used without going chemical route was a large 75%+ water change during which I removed as much BGA as possible, I did a gravel vac wherever there was no plants, cleaned out filter media (in a bucket of "clean" tank water) and completely blacked out the tank for 5 days.
When I finished the blackout I did another 75%+ water change, reduced feeding, reduced ferts and removed any dying/decaying plants. I would make sure any "mulm" from fish waste and decaying plant matter was removed, and increased flow. I kept an eye on all parameters and kept everything stable. I reduced photo period to 6-8 hours, and made sure no sunlight was getting into the problem (corners mostly) are of my tank.
After I started seeing no signs of it returning, I added new plants and began using small amounts of substrate ferts and dry ferts, slowly watching plant response, building up ferts until I reached a happy level of growth, with minimal algae/BGA growth.
Light alone is not why BGA outbreaks occur IME. Low flow and lack of NO3 is just as bad as too much light in terms of BGA.