Hi there!
I just noticed no one has replied to you as yet and you must be anxious (I know I am with my own little one's issues!) so although I'm pretty new to Axolotls myself, maybe I can at least get the ball rolling for you :happy:
I have no experience on the type of rash you are describing, so cannot comment on that, I hope someone with more experience can. A photo of it might be helpful for someone to see what it could be.
A wild guess but I'm just wondering if a tea bath would help with her rash? I suppose it depends on what is the cause but if I've understood it right, at least it wouldn't do any harm, it's supposed to be quite gentle treatment and good for minor skin irritations. Someone with more experience might be able to say more to this. I've never used it myself so not sure. The instructions for it are somewhere on this page but I cannot remember now where...
As for the temperature, how hot has it been in your corner of the world? And what is the temperature of your tank? If it's gone above 24-25 degrees Celcius, then that is a problem and can definitely cause heat stress on your axies. Also, if the temperature has been fluctuating a lot, maybe due to air con or you trying to keep it down, that would cause stress as well. Steady temperature of 14-18 degrees Celcius is ideal (which you probably know already), but even warmer temperature is bearable short term as long as it's steady, the constant ups & downs cause more stress, I've read over and over again here and in the FAQ of axolotl.org. Well, as long as it doesn't reach the critical level of 24-25!
Fridging might not be a bad idea at all, I think. Someone here said, "whenever in doubt, into the fridge!" and for what I've read, it sounds like a good plan. The solitude and very cool temp of 5-8 degrees Celcius will help her relax and start to recover. It will also slow down her metabolism, so not eating is not such a huge drama. There is a great photo guide here for the fridging process, helped me a great deal to do it right (my little guy is in the fridge at the moment as well while I'm trying to figure out what's wrong with him):
Axolotl Sanctuary
Hope this helps, and someone with more experience corrects me, if I've said something that's not right!
ALl the best for getting your axies back on their happy feet and smiling again! :happy: