if there wasent wt loss i would think it may be a turn in the weather ive got some how go off feed for a bit in the winter despite the heat lights and all, but they dont get skinny, snakes starved for months can still grow, just read that somewhere, i think reptiles mag? but the wt loss is bad, id double and triple check your husbandry, try to contatct who you go thim from, see if he has a history of going off food, and last but not least a trip to the vet would be ideal
keep us posted!
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