We used to rank really well on our top keywords

2-3 weeks ago we have dropped 1st page positions to 30-40 place on serps, and some other keywords we simply finished. We seem to have been caught in a filter, which we believe is called minus 30 filter(not sure if that was the one though).

Could you guys advice me on what is wrong and what could we do to fix it? We are concerned as almost all of our sites uses the same structure. Any ideas?

Thanks in advance

It seems plausible that the +30 penalty is an encouragment to use adwords to regain the traffic you once had from organic serp.

List this idea among other possible causes.