Snake mites are parasitical. They are also easily treated. If it happens again, assuming you still have snakes, soak the snake in tepid water for about twenty minutes, then add some betadine and let him soak for another twenty minutes. I use Rubbermaid boxes to soak snakes in. They have lids, so the snake can't wander off.
While the snake is soaking clean out the cage. Throw out all substrate. Then clean the cage with a bleach and water solution. Plastic and ceramic cage furniture can also be sterilized in this way. Rinse thoroughly, before setting the cage back up. Wooden items, like half-log hides, cannot be cleaned in this manner. So, scrub down any wooden items in the sink, than bake them in the oven at 200F for about an hour or so. Let cool before placing them back in your snake's cage.