I don't think the show is this moralistic, but maybe Brock got into his mom's meth stash. His sickness has to tie into the story somehow.

It would be absurd if Mr. White did it. It also seems too sloppy for Fring. Maybe it was Jesse's handler acting on his own.

I didn't buy the Ron transformation based on what I saw of Tammy I,
though I thought Nick Offerman nailed it. Chris just seemed like a bad
cartoon character. Ben trying to turn the 720 crew into grown ups
was too reminiscent of getting April and Andy to clean up their
apartment. The character bits I liked were April…