I'd try to avoid making a form with so many unlabelled fields, as a general rule.
However, if you have to use this, I'd suggest that you
have the default text of each input in each new row be descriptive of the input type.
So instead of 6 empty input fields, have 6 input fields where the value is there, but is grey, not black, to show it is default text.
Input one would have the value "First Name", user two, "Last Name", and so on. You should then use a javascript which clears the default text when the input field gains focus, and replaces it when the element loses focus, if the element has had no text added.