When you don't have water on top of the feed, it will mold within a few days. It starts to stink by that point.The room my FF is in smells really sour and gross, but when I smell the feed itself it smells better. I've noticed if I let it get too dry the smell is much strong and much stinkier. I just use the one bucket method. My chickens still love it no matter how smelly it is. But I don't offer them any dry feed. I bet yours would still eat the FF if they didn't have the other available. (though I'm not sure I'd feed vomit-smelling stuff).
Side note: I used to live in KG!
My chicks are showing the new ones to eat it
