Paying off a collection should never hurt your score.  It does happen sometimes if something is coded wrong.

A PFD is a pay for delete.  You offer to pay if they delete from the CR.  If you PFD and they accept your score should go up, depending what else is on your report.

Since the other is already paid the only thing you can do is GW.

I would start by sending a simple DV letter to them...I found these accounts ____  ____ on my credit report.  Please validate.  There is no time they need to respond, they cannot continue collection activity.