Missing Exhausted Leads

Hello!

As of last week I had setup smart campaign filters to display my exhausted leads within a specific stream of my nurture program. When I ran the report to see applicable members, I got a total quantity of X. However, after running the report today, I am now getting a total quantity of Y which is much lower than the prior week.

Is there something in Marketo that could effect my exhausted leads and cause them to no longer fall within my report? I know content can be added to a stream which would affect this, but Marketo does not provide an change history log for changes made to streams.  So I'm not sure if this is the direct cause.