Dj and god memory leak in rails application

We have delayed_job to handle background processing in our app. God
monitors the more-memory-consuming DJ workers now and then and cut them

This setup has been working perfectly for months with daily deploys. Now
today, suddenly all the workers once they are started consumes 400+ MB
memory each. There were no deploys in the last few days.

What could have gone wrong? please help. The app is running on Ruby
1.9.2 with Rails 3.0.5.