Heroku dynos and authenticity_token

Hi, new to thoughtbot but really like it so far.

I have built a basic app and deployed it to Heroku. Originally I had one dyno but just bumped it up to two. Now I get authenticity_token errors when the dynos change.

Is there a good resource so I can understand how to overcome this? I am still learning all this stuff, obviously, as I am here at thoughtbot. I thought something like authenticity_tokens would get figured out by rails/devise and heroku. Or have I just done something wrong and buggered it?

Id appreciate any guidance.