The body is a complex chemical factory with lots of interactions. Imbalances in the ratios of these trace elements can cause lots of problems with similar symptoms.
In particular :-
Iron (and not just Ferritin) (heavily updated 10/10)
Adrenals (heavily updated 10/10)
Vitamin B12, an external link talking about this (New 10/10)
A posting from the list about B12
Here's where I learned all I know about B12 deficiency:
I highly recommend you join wrongdiagnosis and participate in this
conversation thread (it's turned into a support group). That your
serum B12 dropped so quickly might be a bit suspicious. There's a
possibility that you are predisposed to a genetic sort of problem with
B12 deficiency, something to do with autoimmune. Easy to deal with,
you just supplement.
Lots to follow when I have time!!!!