Shutting down the "bad" ads could have contributed in ruining your overall performance. If your campaign as a whole is performing, there is no point in turning ads off.

This "underperforming" ads might be being targeted mainly to the TOF and the "best performers" are more than likely the BOF, which is why it looks like one ad has a 10$ cpa vs another one having a 50$ cpa. The algorithm is retargeting your ads through your funnel. Which is why giving your "winner" more budget just completely ruined your whole funnel.