The best thing to do at this point IS NOTHING AT ALL
You hve begun what I call "beginner futzing." Futzing is doing nothing in particular to a tree, but doing nothing in particular until you kill the plant
Quit with the seaweed. It's not doing anything except making you feel better. It's not helping the plant and could be complicating things. The soil on your tree is most likely in need of a change, but that can't be done until the plant is recovered--which could take a year or two.