Nothing wrong with being concerned when you notice something off. Doesn’t hurt to try an entice them by trying different things . Nice warm soup maybe the ticket to a nice meal they would enjoy.:)
Maybe they needs a little fun, get some Romaine leave whole and hang it in their run or coop or a head of cabbage. If you have tried giving them warm duck soup you might try a little to see if they like it, some of their feed with warm water and a sprinkle of meal worms over top or chopped kale?