There would be quite a good chance of transmission if two snakes shared a tub, even with the divider. That divider isn't air tight and fecal matter can easily seep under.

Sorry about the findings, Emily. I hope they respond well to treatment and you can start seeing some good growth Can't believe they have 3 types of parasites though, wow... Must have been some pretty unsanitary conditions they were in before they came to you. They have a great chance with you though, you're a good snakie momma.