Well some humans have a few petechiae without there being any apparent cause for concern, so maybe it's like that in snakes? Just happens...?
As far as any dietary deficiency being the cause, I'm assuming you feed f/t...have you used the same source for a long time? It might be that they don't feed their
rodents the "best" (complete) diet, resulting in feeders that lack a little something? But that's just pure speculation in case you feel like adding reptile vitamins.
I breed ASF’s & Rats... feed Mazuri Rodent and they snack on my left overs