GEEZZZZZZZZZZZZZZZZZ, thats a whole lotta Sweet Flag going on,

I was given some two years or more. I keep on looking at it, does not do anything, same amount as when I first planted it?? I have it growing with the iris, then rest of it growing with ribbon grass and obedient plant, GETS WAY LOST WITH ANYTHING BIG OR SMALL GROWING NEAR IT

Maybe add some fertilizer like with the pond lilies in the spring?