Thin content penalty to all sites on GoogleWebMaster account. Is this normal?

I have already read the general info about thin content but I would like to ask to people who got similar experience.

first time received a thin content warnings and lost %50 traffic. The penalty applied all 20+ sites on the account, some are belongs to other people, companies..ext.
It is normal for google to penalise without giving any info that where is the problem. Yeah, it is our job to fix without clue.
No spam content, no doorways, no duplicates, also people like the most sites, sharing them on social media and blogs.
I don't know how to respond this, every site needs an individual reconsideration request, some sites are blogspot blogs with very innocent unique content.

What will be the best action? what is the success rate of recovery?
maybe better to go and find a job as bus driver they seems more relaxed and happier than SEO.

 

Best action, honestly, has been to never add google plugins or script to a site or submit a website to webmastertools.

I know people will disagree, but I have seen more people complain about webmastertools hurting their site than it helping them.

If there are poor backlinks directed to your site, find them, and disavow them. That's pretty much all webmastertools has become good for, telling Google the mistakes they made in penalizing your site.