One of my websites had begun to use Amazon ELB for load balancing.
As long as I see the webmaster tools, the +1 audience has stopped its increase since that time.
In addition, the site has issues too on several Google's services such as Google Wireless Transcoder
In my observatio
The DNS of Amazon ELB has TLS of 60 seconds. Google's DNS caching should expire within that period.
It's turned out that Google+ itself too causes this problem.