i dont think coco is more carcinogen than other mediums
it just releases some elements, which must be taken in count when formulating the nutrition
but all the liquid additives are more or less bad from whati heard .. the manufacturers mix em with several nocive coponents so everything stay fresh/in suspension
thats why i dont use any, like most well informed growers
only base mix(a+b) and PK of any sort are needed to grow fire
even better mix some dry salt or buy some dry nutrients already mixed, and use em with calcium nitrate and mag sulfate
if you dont use any liquid snake oil, PGR's or systemic insecticid then the main concern to get healthy buds is too feed the right way
the way to do this is to recirculate the nutrient solution, and be sure the EC of the runoff never climb
i like to keep it really steady, which means you're on the right spot
if you let the EC of your runoff climb, nutes accumulate in the buds and then it becomes carcinogens for sure