I would use it weaker than recommended if you want to experiment with watering it, and watch for signs of the leaf tips scorching.
But as Tex said, Potassium is very useful to plants in all life stages, especially to help floweriing andthe immune system. Personally I'd foliar feed it as recommended, but humic acid is GREAT for your soil so if you can figure out how much to use, you should be able to get benefits from it.
Keep an eye on runoff pH as well, and if you see anything funky going on, flush first and ask questions later.