I've heard a lot of good things about Sohum. I am currently using Kindsoil and not expecting to fertilize all the way through flower, although I have some teas ready and top dressing if need be.
It seems to me if it's an organic time release you should be good to go for top dressing at any time. I grow autos and amend my mix with an organic dry granular and top dress at week 7. I know it doesn't release until water is added and takes many waterings to dissolve completely. It says it's a slow release and I know it never burns. I've used it on lawn, trees, shrubs, veggies and fruit since 1986 and cannabis since 2014. Cost about seventy cents per plant and never have deficiencies plus I never need cal-mag.
The old maxim is if it works for you then it works. I'm a newer grower in the first place, so mostly I'm just repeating what I've heard, but some people say they like to have more control over what the plants get and when than they get it than the time release fertilizers allow.
I like the old maxim and am glad I found my growing "sweet spot." I've tried Kind soil grows and synthetic nute grows that gave