It does kinda seem like something is missing here. But I do have a couple of questions....

Would the snakes have to be too hot either at death or afterwards for their eyes and heads to have sunken in/ looked dehydrated, or could this happen after death at the temps that he had in the tanks?

I'm just wondering if it was a possible temp spike that lasted for some time since the OP posted that "they were fine 7 hours before" (paraphrasing here). Maybe a lengthy temp spike happened while he didn't see, although would this lead to death in the same way to both snakes in different set ups?

Or, if they could have "dehydrated" under the temps that he listed, maybe their was another cause of death unrelated to temps??

To the OP... how long have you had these corns, how old were they, and did they come from the same breeder/place? I'm just very curious as to what happened....