Oh....Celiac Disease. IMO, your B12 is low and I would try to be more aggressive in bumping it up. I've met too many people with low-normal B12 who were told the same thing only to find that B12 really helped them. Depending on the form of B12 you are taking, you may not have what you need to convert it to a usable form. Also, if there's an imbalance of bacteria in your gut, the bad stuff will eat up the B12. When taking B12 orally, especially in your case, you need to take a high dose in order for some to get absorbed. There are/is a liquid spray that doesn't have to go through the gut that may be helpful for you.
On the vitamin D....a low normal is not optimal. Spend some time reading about vitamin D at
http://www.vitamindcouncil.org/
With zinc....there's a relationship with copper and you doc should check the zinc to copper ratio. If you search on copper in this site, there's a couple of threads on this topic.
Apparently your body is able to maintain those blood counts with a lower retic. B12, folate, b6, copper, iron are needed to make blood. B12 is critical to nerve and mental health also. It can take years for symptoms to show up when someone has low, low-normal B12.