Relax, first of all, they usually go to the bottom when there about to shed, no big deal, the tongue thing, not sure can you post a pic? It could just be dark red, their tongues can change colour very fast! From white to cherry red! If she is shedding she might just be grumpy, also her keeping her mouth open is usually a sign of being to hot, just like what a dog does to cool off. If she's with another gecko, I'd separate them, don't want her bullying, or getting bullied by others. Make share she has lots of spots to hide and not be stressed, I know how you feel, I freak out about anything with my gecko, don't worry, just keep an eye on her, make sure she's hydrated and don't worry to much about food, they can go a while without anything,that being said, don't stop feeding her, make sure she as good as you can get her! If anything gets worse, do go to a vet.