Im sorry to hear that but unfortunately for me, we dont really have a vet that focuses on leopard geckos here. So I dont think I can do anymore for her other than take care of her and make sure shes comfortable and just wait and hope that nothing bad happens to her.
Do you think that is contagious? Should I separate her from the others?
Thank you for your concern.
. 
There should be a vet clinic or maybe even a veterinary university in your surrounding- check for these, as there are almost always people with experience in such places..
At least a "normal" vet should be able to carefully take samples of the poop and a swab of the pharyngal /stomac region and send it to a lab for testing.
You can also make another post here in GF to ask for a fitting vet in your surrounding.
I can't tell you if she could have something contagious, as this depends on the exact diagnosis- a reason more to make a check-up with a vet soon
BTW my gecko also was only alround 5 months old when he died...
/Rebecca
This is a four month old, not an adult. Enigmas do go through drastic color changes from hatchling to subadult to adult.
While I applaud the taking and checking with a vet to be a good, responsible thing, I think everyone might be hitting the panic button here. If I am wrong, I'll be glad you took her to a vet. Better safe than sorry.
But I want to show you. This is a progression of one of my enigmas, in fact, this is the sire I used in my enigma x enigma thread example.
Hatchling:
Bebe Gecko:
Subadult:
Now:
(His tail is skinny from chasing his girl too much. He's getting extra waxies and supers, don't worry.)
So, they can progressively lose color...and not have it be an emergency.
To the OP, I hope your gecko is in prime health. I hope it's just an aging phase.
But I havent proven yet that she's an enigma. The seller told me that both her parents were sunglows too, unless there was a mix up with the eggs. The only symptom I saw was her bad food striking which I dont think is enough to prove.
