How do I find our API limits and use per application?

I'm hoping someone can help me. :)

We have 3 integrations to our Salesforce org. A couple of weeks ago we appeared to hit our API limit, according to the error message received when one of our applications stopped working. I have been asked to find out how many API requests are made per day, for each application, but I don't know where to find this information. 

I can see our API Requests, Last 24 Hours and API Request Limit per Month, but want to find the usage broken down. I've downloaded the login history, and can see logins made by the integration users, but I don't think the numbers match as we do not appear to have enough logins to go over our limits.

Is there any other help available to show me what API calls we have?

#Integration