@jc76 yes, as you say. In general you can get most nutrients just by having a good diet, with vitamin D being perhaps the most difficult these days. And some vitamins are very safe, like vitamin C, the body happily passes excess right back out.

Even Mg can be a little tricky since different supplements absorb better or worse so the blanket recommendation of 400mg isn't enough. I take a little Mg at night to help with sleep, but 100 mg of magnesium glycinate is as effective as 400 mg of magnesium oxide. A handful of almonds after lunch or dinner is a natural way to get Mg, too.

You don't want to be short of K (potassium) but in general eating some fresh fruit and vegetables daily is the right way to do that, and too many in supplements can be dangerous. Also the general advice is not to take calcium supplements, again dairy products also dark green leafy vegetables, are easy ways to get it naturally.

Overall diet can facilitate health and a simple, balanced diet is far more important than we've generally appreciated. Did you know that vitamins weren't even discovered and named until the 20th century? And even then they weren't considered medicine. Doctors are taught very little about it, and it is not considered a standard topic of discussion, is outside of standards of practice so discourages mention of what doctors may have picked up even outside of medical school. You really want an MD who also has nutritionist training but that is fairly rare. A nutritionist who is not an MD and so can't even see your records is already working at a disadvantage in both education and information.