The answer to your question lies with the University and how it views "legitimate educational interest." Thus, while there would be no issue with permitting the original faculty member access to the grade change and the re-evaluation that relates to it, any such decision rests with the institution.
Institutions are required to define "legitimate educational interest" in their annual FERPA notice to students. This is the basis for determining when and if a faculty member is permitted access. § 99.31(a)(1) and § 99.7(a)(3)(iii) of the FERPA regulations will provide you more details relating to this issue.
Also note that, under FERPA, there is no "right" on the part of faculty members or staff to access any student education records. As explained above, such decisions rests with the institution and is based on its definition of legitimate educational interest.
I hope this is helpful in answering your question. You can find the above cited FERPA regulations on pages 159 and 156 of the . You can also find a model notification of FERPA rights in Appendix D of the Guide, starting on page 187.