I've seen barley wine aged 6 months, that then carb'd fine without adding yeast, and 58 is a decent temp for yeast...
but yeah, maybe you just managed to secondary bulk condition too well.
no sediment in the bottom of the bottles right? if yes, they carb'd and it leaked out, if not then yes you can open each bottle, toss just a few grains of yeast in, recap and cross your fingers.
its not gonna take much yeast at all...I'd try to use a half satchet among the 2 cases...but I've never had to do this myself *knock on wood*
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