Question

did walter poison brock

Answer 1

Yes,Walter  poisoned Brock to turn Jesse against Gus Fring
It's an insidious stunt that works. In all actuality Walt harmed Brock , only not with ricin. All things considered, he utilized a Lily of the Valley plant which was filling in his patio. The impacts of ingesting the bloom mirrored the ricin that Jesse accepted Brock had eaten.

Answer 2

Yes, walter poison brock 
Because there was a luncheon with Andrea, Brooke, and Jesse, and the invitee was Jesse, who was in his apartment with Walter, and they sat together having dinner, and Jesse's surprise appeared that Walter had taken a ricin cigar from his clothes, and this became clear evidence later that Walter was Brooke's killer using poison in his food.