When is it time to see a Dr for a check up?

Patient: I’ve noticed my nails are a bit pale and brittle, I used to have hypothyroidism but have stopped medication since my last checkup showed it had been cured. My iron count is good and I have low magnesium and Vitamin D, is there any serious problem if so how do I find out?

Symptoms: Brittle nails, dark pink near end (white) pale above only on some nails. I have no pain anywhere in my body or any other serious symptoms.