I's it normal for an axolotl to be normal all day eating normally going about his bushiness and then for no apparent reason start giving signs of stress (the hook shaped tail tip) ? This goes on about 20 min and then he is fine again. All the watter parameters are fine temperature is a bit lower than 20C. He also has a no food day once a week and he seems to hate it since he is lazy and stressed most of the day.