I agree with you, it should have taken them 20 minutes tops to arrive at those verdicts.
They ran a half-baked cut-throat defence through their barristers' closing speeches with each claiming the other two meted out a violent beating while they reluctantly played a gentler, more passive role as they were fearful the other two would turn on them if they hadn't. It may have had some traction with the girl's defence but for the audio evidence which revealed she was the most enthusiastic of the three and of a witness who described her as evil and sadistic.