“If one suffers no symptoms from a disease(e.g., high blood pressure, a lump, etc.) but is diagnosed with it, should one just not treat it until symptoms begin to surface?”
You missed my point. Asymptomatic patients should be treated to prevent complications. So I don’t know what you mean by a lump? If you mean a benign tumor that doesn’t have to be removed- what kind of complication is there? On the other hand, hypertension & celiac have complications.
If someone hasn’t yet been told to go on the GFD, there is no reason to start on your own before Pesach.
A few more weeks isn’t going to make any difference.