I feel very sorry for Marcus.
I do not know the full details of his symptoms, but I do know that for years he has had migraines and other problems.
For years, I was the same, but I was not a sportsman, so I didn't pressurise my body. Imagine my surprise when at the age of 55, I was diagnosed as a coeliac. This means I'm allergic to wheat, barley and rye. The reason is that when something is wrong with your gut, it starves you of the vitamins and nutrients you need. It often manifests itself in very strange ways. With me it was severe dandruff, migraines, mild depression and wind.
Now, according to statistics one in hundred of us are coeliacs, but it is very surprising that there are no top class sportsman, who suffer from the disease.
Perhaps Marcus is one. I just don't know, but the pattern of diagnosis is typical of the one, that most coeliacs go through before eventual diagnosis.