Has Dr. Ben Carson weighed in on this subject?
Yes.
A few nights ago on Hannity he and some of the other docs who are Fox Contributors were weighing in and demanding her medical records.
FWIW, here is another interesting story. Apparently the Secret Service has blown the whistle and told some journalists that she really does have a medical problem.
http://www.infowars.com/secret-service-whistleblower-hillary-has-major-neurological-problems/