Starting and ending dates seem to be an issue for many people. Are the database fields datetime data types? Then check if the code is considering the time portion of the data.

For example, starting 01/01/2015 and ending on 01/31/2015

Parameters passed from SSRS are interpreted as midnight. Unless the code considers that, the data from 01/31 is left off.

As for caching questions, take a look at this article.

https://msdn.microsoft.com/en-us/library/ms155927.aspx