Workflow Update on Requisition

Summary:

Wrong workflow used on a requisition, error discovered after job was posted and candidates applied.

Content (please ensure you mask any confidential information):

Hey Community! We have begun our biggest recruitment campaign of the year, and have spent the last few months creating and testing a specific workflow to be used as part of this campaign. 
When the requisition was created and posted, the default workflow was used, instead of the specific created workflow. 
We do not (appear) to have the ability to update the default workflow to our new workflow due to the requisition being posted, with already over 2200 applicants.