PBNs gradually being de-indexed, money site fine

Hi,

I made a small PBN with around 10 sites last month. Seven of them have links to my webpage, and when I started they were all indexed by G. However, over the last week or two, three have been deindexed. I haven't pushed much (if any) content to these pages in the last couple of weeks but I don't think that is why. As far as I can tell my money site hasn't been penalized, since it has pretty maintained its SERP and is still indexed.

What could be the reason for these sites being de-indexed? Have Google automatically found out that these are PBN sites or could it be for some other reason?

Thanks

what are you using to tell you they are deindexed? If you just searching for the domain in google, and they are not showing up, they might have just temporarily dropped out of the index. Make some social signals to them, and give it another week before you start wondering too much

Do you use redirection plugins or scripts ?

What's the date when the the deindexing started? I lost almost 200,000 indexed pages on 8/16 on one site, but not too worried since Google's corrections happen often.