Site penalized August 12th 2021

I have a WordPress multisite 15 domains, local news. 4 of the 15 sites seem to have been hit by the same penalty and have not recovered. No manual action so seemingly an algo penality. They are using the same structure, theme, design, etc. But unique content on each site. The penality is this... The ~5 top keywords for my homepage no longer rank, no where to be found in results, including the brand name. If you search the brand name with no space between the two words it's still number one in results. The homepage code/meta had not been changed in about a year, it has dynamic content for recent, trending and featured articles.

I have done no intentional black hat things. I've never paid for backlinks or added any myself. It was all natural. I did notice a bunch of backlinks from sketchy Blogspot sites so I disavowed them.

I'm not sure if some targeted me with bad links or maybe there was an algo update that flagged only the 4 sites for some reason?. I'm still dumbfounded as to what happened and I'm hoping by now people might have more insights into algo changes from that time and might be able to give some tips on things to check. I prefer not to share the domain names. Any tips are appreciated.