Tomcat 5.5: Webapp monitoring options

One of our production Tomcat boxes runs two webapps. One is ours, another is a black box app that our vendor supplied to "help" with our app.

We are, unfortunately bumping up against memory limits on our production box, and I'm working to add RAM and have Tomcat start with more memory available for the JVM. Before I do this, however, I'd like to see which of these two webapps is eating up all the RAM!

Is there an option within the built-in Tomcat manager that shows RAM usage by webapp? If not, is there a free solution available, somewhere, that offers this level of diagnostic availability?

If need be, I am open to writing my own lightweight webapp to do it, and have one running on the machine that watches the other two.

Thanks,
IVR Avenger