Spangled hamburgs are super cute! I would always provide a quality chicken grit along with pellets. Some forgo offering when they feed layer pellets, but I find it best to always provide quality chicken grit. Chickens have an amazing talent at knowing what they need. They will not overeat. I normally keep it in a pan on the ground, I have one chickens who has a disability, but this idea is cool too (image provided). You can also offer chick starter to adult hens when they are molting or when they are regenerating new feathers. It is a bit richer than their standard diet but can give an extra boost. Offer it in addition to their normal pellet, and I would use a separate feeder so it is easier to monitor intake. Some people offer it year round, but I only offer during molts.
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Since it is difficult to know which bird or exactly how it is presenting I will provide a few links here. Consider how your bird may fit. Pay special attention to their posture. New Castle for example is very contagious and deadly, it is an unlike possibility, though I will provide for your info.
If the shell is a good thickness and shaped normally that is a good sign. Egg yolk peritonitis can be ruled out.
Egg yolk peritonitis in Chickens
Possible illnesses connected to Pale yolks:
Newcastle disease (ND) is a highly contagious viral disease that affects both domestic and wild birds worldwide. ND is caused by the Newcastle disease virus (NDV), also referred to as avian paramyxovirus (APMV). NDV belongs to the genus Avulavirus within the family Paramyxoviridae. There are...
www.poultrydvm.com
Coccidiosis is the clinical illness caused by infection with the protozoan parasite genus Eimeria (coccidia). The nine coccidia which infect chickens are E. acervulina, E. brunetti, E. hagani, E. maxima, E. mitis, E. mivati, E. necatrix, E. praecox and E. tenella. Most of these parasites invade...
www.poultrydvm.com
Dietary it can be from a lack of greens in their diet.
It can also be from recent or over use of dewormers.
I hope this helps.