Welcome to HCM,
After going through your history,you are having vitamin d deficiency and there are several effects of deficiency in cardio vascular health, bone health,and on immune system.
Benefit of supplementation of vitamin D is confirmed in many scientific studies.
It also depend on your age and other health risk factors.
Your ferritin level reflects total body iron level even though your hemoglobin
level is normal hence iron supplementation given.
Please continue to take vitamin D and once level becomes normal you will feel benefits of it.
There are many causes of deficiency may be diet and inadequate sun exposure.
It is claimed to improve bone health,cardio vascular and Neurological health .
It also improves immunity.
In your case nothing to worry about just follow advise of your Physician.