Nose breathing is not an accurate metric for HR zones in aerobically deficient athletes. Since you don’t seem to be 100% sure of your HR zones they’re possibly wrong. My hypothesis is that you actually went harder than zone 2 and stressed your nervous system in a way that you weren’t used to or ready for. I lose my appetite too when I try hard for a long time (my experience with that would be after power endurance rock climbing workouts). I find that going for a short walk and eating a little bit (like a piece of fruit) will open my appetite to eat more over a few hours. Drinking a 1500 calories shake on an already nauseated stomach would not make me feel good either.
Rest and you’ll recover. Once you’re rested do the following test https://uphillathlete.com/8-diy-steps-to-figure-out-your-aerobic-threshold-indoor/, it’s what the coaches here recommend to figure out HR zones. The feeling better running might just have been a result of increasing your training volume rather than actually fixing your ADS.