Duplicate content may be a issue. but if content is not duplicate then you need quality links not just some low value links. Try to get Relevant...
Some times site ban login info if you not login for a week or more. But if account is new ..Not for a old account holder.
Bring as much traffic as you can..More traffic more chance to become special... :)
may be you are drop some rankings. You should find them and start building new links for those keywords So you can get back to top...
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