My gal also! Last month when she was 18 months she started rejecting the food she would normally eat..and after one month i realized its cos shes teething..her molars were just about to erupt at that time..according to my hub who cleans her teeth twice a day.. Now that they have broken the surface she is starting to eat her normal threadfin again!
I think it's just one of her "moods"? Just give something else for the time being and try again? Or maybe change the way you cook it like add ginger etc? My girl was like that a few weeks ago too! What used to be her favourite food she suddenly refused to eat it and will just throw it away. Very frustrating ！