Wry neck can have varying etiologies; causes that aren't related to a nutritional problem. Deficits in Thiamine (B1) and vitamin E can cause wry neck, but if you do not see improvement over a week or two with supplementation, it's possible the problem is related to something else (exp, metabolic disorders, bacterial infection, neurological damage, etc)
If you wish to continue with the B complex and give it SC, start by plucking a few feathers near the bird's interscapular region (between the wings/ on the back). Wet the area down, tent the skin, and insert a needle (22 gauge will work) bevel up, into the tent, and press the plunger. A small bulge will be noticeable afterwards, which will eventually dissipate into the subcutaneous space, and be absorbed.
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