What does it mean it I receive collection notices/past due n

I have received several notices from various CAs (sadly all accurate charges) but when I pulled my CR, only one item appears as a collection. There are several negative reports, but I know of other debt that is not even listed. Should I go through the DV & PFD process even though these items have not yet been posted to my CR? Why wouldn't the CA report it? I understand SOL, but does a CA have until that time to report the debt to the CRAs?
Thanks for the help!