Existing candidates login to carrer site issue

After launching the career site we faced the issue with logging in of existing candidates.

We don't have any problems with new candidates who applied via the career site. The only problem with those candidates who were cretaed manually before launching the portal.

Problem is the following – 

1. When candidate try to reset their password system asked to ented username, which candidate doesn't know (reminder that candidate was created manually).

2. Candidate try to reset useraname.

3. He enter his email address and receieve email with his username.

4. After getting username candidate can restore password.

5. He enter his username and email, and recieving email with code and link to restore the access and enter new password.