No Plugins Installed Error

Ok this seems to be a weird thing that’s been happening to the plugins for almost three weeks now:

So I installed some plugins from way before, and about 3 weeks ago, I tried accessing the plugins page in the admin portion of wordpress. And all of a sudden, there were messages in red saying that most of the plugins that I used were deactivated because it has a bad “header”. I’m not sure what that means but when I loaded the site now, all the plugins seem to be deactivated.

I installed a new Pinterest plugin and it seems to work fine, but now when I accessed the Plugins page again, the same error came out, and now even the Pinterest plugin doesn’t work.

I am not sure but is there like some bug or a security breach in the new WordPress version causing these? Let me know if someone encounters the same thing.

The site is http://www.lynne-enroute.com

Thanks!