I checked, and my B12 was 572 pg/mL in March of 2020, and 532 as of last week.

So it does seem to be dropping, assuming it's not a test artifact.

I wish I knew what to do to go back to the way things were; I don't think my doctors do. Should I stop the supplements, or add B12? I just feel in my gut that the new neuropathy symptoms (shocking pain+some numbness in limbs) are related to the iron supplements.