Diagnose problem with cron job and php application

I have a php application that runs a cron job nightly. The cron randomly assigns reviews to our user database when a new order is placed and sends a notification email to reviewers, sends reminder emails after 24 hours for any uncompleted reviews, reassigns reviews not completed within 48 hours and sends me an email listing all deleted review requests and reassigned reviews. The cron job continues to run nightly, however it is only sending out emails for new review requests, not the other emails. I need someone to correct this. There aren't any issues with the email settings, as emails are going out from the application, so I don't know if the issue is with the cron job or the php in the application. I need someone to fix this for me.