It's good to be an educated consumer about these things. I'm a proponent of organics, but I don't like the shrift that heavy metals in organic amendments/soils receives. If you are concerned about the heavy metal content of your flowers, the short answer is, if you use a known, clean source of mineral salts, like Jacks a/b,
Maxibloom, etc, (and a clean media like most coco) you will end up with less heavy metals than in almost any organic grow. And I really hate that. Look up jacks and
maxibloom (or flora, floranova, most GH products are very clean) here
https://apps1.cdfa.ca.gov/fertilizerproducts/. Then, look up your rock dusts of choice-just search by basalt, glacial, azomite, diatomaceous, greensand, etc-there aren't a whole lot of samples for some of them. Now, look up "kelp meal" and "crab meal" in that database. See what I mean? Kelp meal is part of the reason a friend failed his heavy metal test for a dispensary grow (some liquid kelp products are safe though, you just have to check-Age Old Organics liquid kelp for example.) A lot of the most popular amendments in organic soil recipes are really high in arsenic, cadmium, and/or lead. I'm now avoiding all rock dusts-I still use gypsum and langbeinite depending on the recipe, you can find totally clean versions of those. I'm working on a batch of no till soil right now and am aiming for as little heavy metals as possible. Honestly, some organics proponents are so freaked out about pesticide residue while their soil builds up with more and more heavy metals each year, probably causing far more damage than the thing they are worried about.