MS or Vitamin Deficiency

About 2 years ago I went to a neurologist because my left hand was numb and ached, I was dissy and extremely exhausted.  I have had unexplained itchy skin on and off for almost 10 years (no allergy meds or dermatologist helped).  The neurologist did tests and said my ferritin & B12 were normal but on the low side so he had me take supplements which I currently do.  I did do a nerve conductivity test and had multiple places where I had nerve damage, including both arms and legs, and neck.  He didn't do an MRI at that time and said that my symptoms were because of a vitamin deficiency. All of the symptoms went away after I took the supplements and I have felt great until recent.  

Now two years later my symptoms are back and have a new neurologist who has done another round of testing.  This whole process has taken about a month to complete and now my symptoms seem to have gone away.  So far I know that all my blood work is fine and my vitamin levels are all within normal ranges.  He did say that the B-12 and D were lower than he would like to see so he is adding to my supplement list.  I have extensive blood test to rule out most everything except MS.  I did just recently have an MRI with contrast that I am waiting on the results.  

Can a vitamin deficiency be present if your numbers are within the normal range but on the low side and would you have these symptoms?  I am concerned that this new neurologist is going to say it is vitamin deficiency again and not rule out something more serious? I also see how MS and B-12 deficiencies symptoms can mimic eachother so how do you really know which one it is? Also, why would someone keep having vitamins in the lower range of normal with doctors that just keep telling me to take supplements?  Shouldn't they be wanting to know why?    Sorry if this post is confusing as this whole experience has been a very confusing one.