Molting can cause lowering of feed consumption, contrary to what they need. A couple of mine are in full molt and miserable. They hide all day, eat very little and poop watery, nasty greenish stuff, which is what happens with low feed consumption. I am trying to feed one hen daily special stuff I cook because there is not one ounce of meat on her keel and due to her advanced age in this bad molt (she blew all her feathers at once), I'm worried I'll lose her. Another is starting to act the same way. So, the molt depletes them in so many ways, especially as they get older.
There is always a normal cecal poop that smells atrocious, of course, but a molt and different eating habits could possibly change the smell of the everyday poop. Worms could also do that, I suppose, but I would hesitate to worm a molting chicken, the molt is already so hard on them.