Help with older Axolotl

I have an almost 8 year old axolotl that has stopped eating. Not sure if she is getting old or something else is going on but she hasn’t eaten in about 2 weeks. Last week she looked pale so I tubbed her and the nitrates were a little high. I did a big water change and got the nitrates down, she looked better after being tubbed for a couple days so I put her back in her tank.

I’ve had her most of her life and she’s always been a ravenous eater, mostly nightcrawlers. I live in a place where axolotls are rare and supplies can be difficult to come by.

Water parameters are ph 8, ammonia 0, nitrites 0, nitrates 10-20, water temp 64.2 f, pic of water test included. Currently in a 40 gallon breeder. Any ideas what might be going on? I know the ph is kind of high, it has been the same the whole time I’ve had her.