So I started out with chickens a month ago or so.
I bought 1 white leghorn, 2 deutsche sperber (look a lot like plymouth rocks/dominiques), and 1 black/brown leghorn, all of which were about 22 weeks at the time.
The black one was the first to start laying every now and then, until it once layed a very thin-shelled egg and then started to lay shell-less eggs, which were eaten as well, since they stepped on it. I have since supplied oyster-shell grit and some vitamins (especially D3, within conservative bounds) to help absorb calcium. Sometimes I also grind up shells and put it in their feed.
For a week or so the black one has stopped laying completely (I assume she stopped because I can't find even the egg-"bag" that sometimes was still laying around). The sperber are laying close to every day, they just started, and the white one has been laying an egg a day for the past 2 or 3 weeks.
I feed them with a mix of corn, peas, buckwheat, linseed and sunflowerseeds in a ratio of 30:30:30:10 (10 is the oily seeds), which I grind up. The mix is calculated to have about 15-16% protein. They have a big run with lots of opportunity for foraging and insect hunting, which they happily indulge in.
I'm not sure what is going on with the black one. Is it normal for egg production to be so unsteady or is something wrong with her? To me she seems quite healthy. Only yesterday she was panting a bit, but it was pretty hot outside (30°C/86°F). She isn't panting with an open beak today.
There were no new additions, and their life here should be rather stress free (apart from an owner trying to pet them every now and then

). They don't get too many treats, every now and then I'll bring a banana (thanks to the supermarket that are throwing them in the bin), which is pretty hilarious to have 4 smacking chicken pecking away at a banana
The only thing that maybe seems a bit off is that the black one has slight streaks of droppings on her butt-feathers, but I haven't noticed any diarrhea-droppings in the coop.
I've considered maybe she has worms, but then when my cat had worms it was very lethargic, but the hen isn't, at all. Any ideas? Thanks!