Breaking Bad: why did no one point out that Brock was NOT poisoned with the ricin?

Why didn’t Walt point out that Brock was NOT poisoned with ricin?

Rewatching the series and there’s something I don’t get. Jesse realizes that Walt had Huey lift the ricin cigarette off of him. He jumps to the conclusion that it was Walt who poisoned Brock after all and goes crazy.

The only issue is that the hospital EXCLUDED ricin as the cause of the poison, so why doesn’t anyone point this out?

I know that Walt did actually poison Brock, but not with ricin, but Jesse has no way of knowing this. I don’t see a reason why realizing Walt had the ricin cigarette stolen would immediately lead Jesse to know that Brock was poisoned with a berry when it was perfectly reasonable that he picked it off a common plant and ate it.