I was thinking along the same lines... I would not have butchered mystery meat so quickly. Feed them out, deworm them, make sure they have no serious illnesses that aren't showing, etc... Then go ahead and butcher for food. I wouldn't even feed poorly looking auction animals to my dog.
I wouldn't be concerned about growth hormones. Wormers, medications and the like not approved for use in animals intended for human consumption or requiring a waiting period on the other hand are a real possibility. As is sub-par feed, which not only can contribute to food borne illness but definitely affects the taste of the meat. So even if it doesn't make you sick it may end up being 33 cent bacon that tastes like ... well, 33 cent bacon. LOL! But it's your pig and your body.
I'm curious though, if they were vet "approved" how did you not know what they had weren't "tumors"?
I would have thought that was something the vet would have mentioned during the exam.