This seems like a messaging problem?

"Password does not match our records for username/email XXX. Please check that both password and username are correct."

Responding to below This reads to me like a more verbose version of "Incorrect username or password."

Note this version is not wordsmithed and could probably be done better but the goal and inherent difference of this to the original is to let the user know that the username exists and that its the password which does not match.