This is interesting. I"ll make sure to follow up with clients that have/will recieve vitamin injections.
I discussed this with my continuing education teacher (Basic Repitile Medicine, Veterinary Information Network) and she had said that perhaps it was from one of two things
1)lack of peripheral circulation ie, the leg was immobilized for some reason (like a cast), or husbandry wasn't up to par, specifically temperature... any other reasons that circulation may be compromised.
2)some injectables are made specifically for intravenous usage and do cause necrotic lesions if outside of the circulatory system. While many drugs are routinely used "off-label", perhaps there are vitamin preparations that do cause this reaction.
It is difficult to explain why it would take 2-6 months post injection to slough the skin. 2 months maybe, but 6 months would surely be related to inadequate husbandry, since any necrotic process would have normally finished in this time period. Cool temps delay everything.