You will see a big turn around.
Aside from the calcium issue eggcessive mentioned it can also delay the development and onset of lay as it is too low in protein for growing birds. Feathers are made of 90% protein and it's amino acids. Young birds go through a lot of mini molts before they get their adult feathers. It's important not to diminish the protein and vitamin/mineral content of their ration with low nutrient treats like scratch or corn. Some breeds or individuals may be effected worse than others. Which is a statement that is true across the board about everything our flocks may face.
Since I always have mutli age and gender flock, I always use flock raiser with 20% protein and 1 ish% calcium with oyster shell on the side free choice for layers. Majority of my birds are dual purpose so do better with more than the average 16% in most layer. Also it's just easier to feed everyone the same thing in addition to being what I can get, at a price I can afford, with a freshness date in an acceptable range, that meets the needs of my whole flock at a happy medium. However, 22% protein was shown to give the best hatch rate and so sometimes I cheat and add in turkey starter. I might do that during hatching, but also during molt. Most my hens recover faster and some return to lay sooner. But I'm not suggesting go overboard.
If you think the rest of your flock is thriving now... just wait until you make the switch!
That is a weird bumpy bumm, I have never seen before. Thank you for sharing, so we can all learn!
ETA: I might offer a little yogurt and scrambled egg as nutritious treat to assist recovery. Of course chick starter or flock raiser are the best food choices. Good luck!
