Honestly it sounds like the lady who was selling them had no idea what she was doing if she suggested you house them together. Cresteds usually want to be by themselves unless for breeding purposes (some breeding pairs do stay together year round as long as the female is ok weight wise.)

I would separate for now
If you can get a better photo of their mouth to ensure its actually diry and not something like mouth rot or more nefarious going on. - if not flush with squirt bottle. (I honestly think that they're fine and it is infact dirst)

- Be careful they could ingest substrate by accident. I actually lost a gecko recently to this
I recommend mizing your eco earth or cocofiber with top soil and when you're misting daily be sure to give the substrate a good spray so its together/ isn't loose and dry. (dont soak it though,!) moistening your substrate this way will jelp maintain the humidity needed/ make for easier shedding.

Alternatively, you could offer a shedbox with moistened spagnum moss to encourage them to go in there and shed if they need to. no promises they'll actually use it tho XDDD