You all have stated some thingsi just now came to the conclusion of. Perhaps there were two crimes. Perhaps ink did give some inmates a cocktail.

I was thinking that the reason a deal was struck might lend it self to Ink or Radon labs having some contract with the prison. Maybe they were allowed to test certain drugs on inmates on death row. Ink may have threatened to talk about this so a deal was made
Maybe the gas from the cracks have to do with run off from radon labs chemicals being improperly disposed of.

The cells had "print outs" of drugs taped to the cell gates. That means the drugs were administered before the world went to hell and lossed power and the prison was overrun. The black ink written on the paper, probably Inks doings post Zday.

The chow hall had all the doors and windows blocked by tables and chairs, except one that had appeared knocked down. This would lend to the thought that not all of the prison was aware of what was going on in Roberts cell block.