the resulting ratio of nutes is the key. as long as you can use reasonable doses to get the resulting ration and concentration you want, it should work fine. There are apps that can take the info off your gauranteed analysis labels and do all the work for you. could type in the canna stuff to set your target per nutritional element, then use that with the products swapped out for other brand and you get your dosage calculated for those targets.. growbuddy? i'm sure it's not hard to search for. hydrobuddy? something-buddy, lol.
as far as additives and non-nutrional related stuff, just read the ingredients and make sure you aren't doubling up on anything that is the same or equivalent function.