Illness/Sickness: Sick lottie please help

My Axolotl stopped eating and didnt move from the same spot for about 2 days, so i though i would put her in the fridge to try and make her well.

after a couple of days we checked and there was a pile of orange gunk(maybe sick) with something hard in it(maybe a stone) which is strange beausee she has sand in her tank.

she is back in her tank and seems to be more active but she still doesnt want to eat,

what do people reckon, should i put her back in the fridge??

water test strip results:-
NO3=12
NO2=0

As axolotls get bigger they start to eat less, i feed larvae under one inch twice a day, larvae over an inch once a day, my six to seven inch miss a couple of days a week and my adults feed three times a week. Axolotls can be very sedentary( depending on their personality), a stationary axolotl could just be content and chilling out whilst one zooming around the tank may trying to be escaping poor waterquality. Its very easy to get overly concerned about your pets behaviour, if the only symptoms youve had so far are a couple of days missed feeding and inactivity, if you have no other symptoms such as injury/fungus i wouldnt bother fridging it again. The fact that your axolotl still isnt eating may be a result of the fridging which will have reduced its metabolic rate and reduced its need to feed.
The yellow stuff you found in its bowl may have been sand, do you have yellow sand? because axolotls do eat their substrate by accident and the stone may have come from the breeders/pet shop.
Its always good to be concerned with the health of your pets, so keep an eye on its feeding and if it continues not to feed for a few more days repost in this thread. Though the stone you saw passed may have been the culprit.