Illness/Sickness: Lethargic, not eating, sick axolotl?

[Demodex]

My 5 year old leucistic female axolotl has become slow, stiff and not at all interested in eating.
I noticed her change in behaviour because she's usually energetic and loves food. She hasn't eaten anything substantial for about 6 days.

I checked the water parameters and the nitrites were a little high, but nothing note worthy. She shares a tank mate (4 year old male) who seems unaffected so I'm unsure if the issue is to do with water quality.

I moved her to a separate container, keeping the temperature cool and doing daily water changes, but she still hasn't eaten and I'm beginning to worry.

Could this be some sort of infection or disease?

 

[21stewarte]

What kinds of food have you tried feeding her?