If the nutrition shop is the high street chain that has those penny sales, can I suggest you don't bother, get better quality ones online.
For Vit C the L-ascorbic acid type is better than the D-ascorbic type although most brands don't state which. Nutribiotics do the L-ascorbic acid as a powder.
B12 - Solgar or Jarrows sublingual methylcobalamin 5000mcg as your level is low.
B Complex - Thorne Basic B is a good one, contains the active forms of the vitamins and uses folate (natural) rather than folic acid (synthetic).
You also need an iron supplement, for a gentle, non-constipating iron look for Albion Ferrochel Iron Bisglycinate as the form of iron. Solgar does Gentle Iron, there's also Blue Bonnet, Now, Source Naturals, Thorne, Swanson.
Remember to start them one at a time, give it a week or so before introducing another. That way if there's any adverse reactions you will know which one caused it.
As for whether you should reduce your Levo, what are the ranges and how do you feel?
If the ranges are similar to mine then TSH is at the bottom being 0.3 but not under range, and 19 for FT4 is near the top but in range, so with my ranges there would be no need to reduce your dose. Where are they in your ranges?