Trump Jr. said in an interview that he did heroin(GuitarPlayer94 if I remember correctly).
Add to that the coke that is affordable if you get bigger, as a band not as a bodybuilder
, and generate some money.
Jeff's play suffered tremendously after 91(post drugs) and he never recovered. Endless shredding is his best friend now. King has always been more disciplined and though he's way less gifted than Jeff he is still a somewhat merciless force at what he does.