I have no idea, but doesn't sound like a mistrial, so must be judge making decision. Seems odd. I am not a lawyer but this is what google told me.
https://www.ccohs.ca/infectious-dise...l-jury-process
Discharge of jurors – During the course of a trial, the judge may direct that one or more jurors be discharged, which results in them being relieved immediately from the jury. This situation can arise when a juror falls ill or faces other intervening circumstances, or where circumstances arise that disqualify the juror. A jury will remain viable provided it has at least 10 members. If its numbers drop below this point, the entire jury may be discharged due either to a mistrial or to election to proceed by judge alone. Discharged jurors will exit the courthouse and arrange for their own transportation home.
I would think Trial by Jury would be better for the defendants, with everything that I have seen and heard so far, it seems likely at least one juror would have reasonable doubt up to this point.