B12: top of range with a minimum of 550pg/ml (although you haven't given the unit of measurement)
Folate: at least half way through range
A good quality, bioavailable B Complex should help raise both, eg Thorne Basic B.
Ferritin: half way through range. You can help raise your Ferritin level by eating liver regularly, no more than 200g per week due to it's high Vit A content, or liver pate, black pudding and other iron rich foods.
As you are supplementing with D3 you should test Vit D yourself if GP won't do it :
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