Hard drive crashed/about to crash, what should I do?

I still appear to have you confused despite my alpha, beta, charlie.  The target disks are coming out fine.  They show lower.  So how would formatting them make a difference if when produced they are fine?  It is what is happening to the primary when it is in use that is the question.  That is when the ballooning is happening.  When in use over say 60 days.  To the primary in-use HD.

You have me completely mystified.  You are not asking for help with Backup software, you in fact have a problem where your SOURCE drive is growing in size unaccountably.  This is far beyond this topic, and would require quite a bit of troubleshooting.  

It could be a number of things, including but not limited to the possibility that your drive is being unwittingly used by others for file sharing (a 'bot'), or other types of malware or virus infection.  At any rate, I am unable to diagnose the issue for you.  I would recommend you consult an IT professional.  If you don't own the full-on Malwarebytes software, I recommend you purchase and run it.  Not just the free version.  Also, do a Google search on the subject of drive size growing unaccountably.  You might find some threads there.

Best of luck.