What’s the limitation here?

Nitrates first pic (after dosing thrive+ yesterday 15mL). Dosing 3x thrive + (last one yesterday, before I water change today and dose again tomorrow). 2x fluval 3.0 lights at max intensity besides blue (15%) 8hr. Getting a 1pH drop prior to tank lights turning on. Could it be phosphates? I do have a high bioload? Not sure where to go from here because you can see good coloring on the plants. One thing I can say is the Ludwigia super red (last pic) isn’t really growing at all. Please any help is appreciated.