I've heard of vitamin injections from a companion animal vet. But I've never had a specialized reptile vet offer it to me when a rescue I took in had RI.
I would keep declining. If your snake ever got to the point of emaciation, then I would suggest tube feeding, which is safer than assist feeding.
I think ball pythons are pretty hardy animals. I believe they can do well in a stable range of reasonable temps and humidity. However, I still think we should give them stable optimum conditions. Some snakes change their habits from the smallest change in temp or whatever else. For example, many of my hatchlings won't feed above 88-89 degrees. Anything above or below and they stop feeding.
And added stress on a snake increases the chance of RI. Their immune system is lowered and directly related to their stress. So leaving conditions to stray away from ideal usually does stress out a snake. Especially if it fluctuates a lot.
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