The article says that drugs were found during the execution of a warrant, it doesn't say what the warrant was for or how the drugs were found during the execution of the warrant. You can find evidence for other crimes when you execute a warrant, you just can't look it if it's outside the scope of the warrant.

Also, even if the warrant was overbroad, the evidence wouldn't get thrown out as fruit of the tainted tree, because a bad decision by a judge (e.g. grant a bad warrant) won't cause the evidence to become tainted in that way. You can exclude evidence because the police broke the law, but the judge isn't breaking the law just by interpreting it poorly. Or put another way, we don't want the police to have second-guess judges' decisions.

If the drugs were in plain sight then the police could get a valid conviction for them...