permissions - Shared group directory with individual user files

I have a mounted NFS partition in which a specific group, say nfsgroup, has rwx for the directory (call it nfsdir). If my user brian is a member of nfsgroup and creates a file in nfsdir, then I chgrp it to say brian (my own group), other users in the nfsgroup can still delete my file. It gives me the rm: remove write-protected regular empty file ‘test.txt’? prompt, but still lets me delete the file from another user not part of the brian group but a part of the nfsgroup.

Is there a way such that I can allow all users in nfsgroup to create files in nfsdir, but also provide a way for members of nfsgroup to protect individual files from other group members modifying them?