You are correct there, for eg., many people are genetically predisposed for Vit. B deficiency as their body cannot absorb that vitamin naturally. If they are diabetic, the problem amplify more. Hospitals provide Vit. B infusion also.
Interestingly, I had the same issue. Stress is the primary cause.
Mild exercise, brisk walking, yoga, etc. in morning help me get sleep early. But, make one wake up early too.
When taking health supplement, check the timing / schedule since some supplement may make you sleepy and vice versa.
Melatonin supplement is used by many, but I never tried. I used an ayurvedic tablet which helped a lot to avoid stress, get good sleep, etc.
One thing I clearly remember, in spite of being voracious non-junk food eater, and slightly overweight kid in childhood (simply because of excess calories of "healthy" food - hence I don't believe I was ever nutritionally deficient), I always suffered from the hang nails (
https://i.pinimg.com/originals/4b/c3/62/4bc36285ace8d5e3d7a4e1eb827ac62e.jpg).
The problem goes away whenever (in past or today) I consume multi Vitamin. It is almost magical thing that I have observed over past two decades or so! Weather/climate doesn't matter, activities don't matter. I take no care of my nails and finger ever except trimming nails, clearing the gunk from underneath (say if I have played in mud) and general soap washing.
Zincovit is a good pocket-friendly alternative that a lot of people use as well.
Then there are other options made by companies like Swisse that cost 1800 for 60 tabs.
In my view there are few things one should look out for when buying multiVit/mineral tabs:
1) the vitamins and minerals should be present in more bioavailable forms.
e.g.
Vit D comes in two variants D2 and D3. D3 is more readily absorbed and utilized by the body.
Similarly, Vit B12 comes in two variants: Cyano cobalamin and Methyl cobalamin, the methyl form is better than cyano version.
The same goes for even minerals: general rule is that organic slats are more readily absorbed by the body; zinc acetate/citrate/gluconate is better than zinc sulfate/oxide.
2) the oil soluble vitamins: A, D, E, K are not required daily. one may overdose and take the next one after one week. Water soluble vitamins like C & B are required everyday; and any consumption more than RDA will simply get flushed away from the body with sweat and urine.
3) try to find if there are lab tested products, so many spurious and fakes, and even the branded ones tend to have lower than reported compositions