FB Page Drop In Serp

Hello. I have a facebook fanpage which was for a specific keyword #1 in google. The competition is really low. The fanpage has around 3000 likes. I have been linking to it with FCS Networker web 2.0.

It was #1 for around a month and now since a couple of days it has been dropping until position 12 today.

Do you know what might be the cause of this drop? Any suggestions how to get it to #1 again?

Also please tell me if you know what is better way to link a parasite - with FCS Networker web 2.0. or to use GSA SER ?

Check your link profile and see if you lost some important links.

well, since I link with web 2.0. ahrefs and majestic, which I use, do not see them so I am not able to check
but if I use 404 checker then most of the links are ok