Thanks for your query.
While thinning of renal cortex
is a sign of kidney
disease it certainly does not mean that your kidneys are dying.
We can slow down the progression of your kidney disease by a number of measures about which your doctor will be able to tell you.
As far as diet is concerned you will benefit from a low salt, moderate protein diet ( a consultation with the dietitian will be useful).
Vitamin supplements are good for your health but will not have any role in preventing the progression of kidney disease.
Hope this helps