When was last module saved or cache cleared?

Using Adminrole, I have created 5 admins for our system. Is it possible to know:

1. When was the modules (admin/build/modules) last saved and by which admin?
2. When was the cache (admin/settings/performance) last cleared and by which admin?

I want to know the above information because my team is using same admin credentials and at times of failures, errors or sudden downtime's, we don't really get to know who was saving modules or clearing caches or deleting certain nodes.

It would be helpful for us if we can track the activity of the administrators as the system is huge and we do need multiple admins.