Changing all text color throughout document - preflight solution?

I am working on a document where the text has been converted (through automatic OCR scan) from embedded to editable. All black text is now a varying mix of CMYK rather than 100% black.

I am using the most current version of Acrobat Pro.

Is there a way to change the color of all text in all text boxes thoughout the document, rather than editing each page/text box individually? I need to maintain colour images and boxes throughout the document as well, so can't just convert everything to greyscale.

I've been screwing around with the colour conversion settings and preflight profiles.
Is there a preflight tool that can detect a specific CMYK value and convert it?
I've tried the correct 4c black, fix registration black, map colour values, etc etc.
Document color is CMYK, US web coated SWOP.

I think part of the problem is that the now-editable text is not being recognised as text?
(it's a terribly-contructed file. I'm very frustrated with it)

Is there a script somewhere that could be imported to fix this issue? I'm comfortable using preflight tools, but have no experience creating my own profiles. There has to be a preflight expert out there with a solution.

Thank you!