Sorry to hear this, it sounds very disconcerting. I think he should see his doctor for a check-up and maybe a referral. While his symptoms may sound strange, I am sure a doctor will take them seriously. It may be that he is suffering from stress but it may also be some kind of brain phenomenon caused by changes in the brain or the blood flow to it. I would not ignore it.
I am not a doctor but I do think that any unusual perception phenomena should be checked out properly.
Do let us know how he gets on.
No idea, but it sounds like he needs to see a doctor.