Yes, but, if I remember the thread correctly, what you said is that you gave him B vit in a poultry vitamin supplement. What @MysteryChicken said was to give him much stronger dose than is available in a chicken supplement. He/she showed you exactly what to give - I think it was 400mg of B2...
If he were my chicken, I would start him on the direct vit B2 therapy as @MysteryChicken laid out. It can't hurt him and it may help. Better than just letter "nature take it course" so to speak.
I have never had to put a chicken down, but I am sure my time is coming. I would do everything...