I lost my beautiful little bantam leghorn through 'internal laying'; I am not sure but I assume that is similar to or the same as egg yolk peritonitis.
She hung in there for a couple of weeks and I tried everything I could to fix her up but to no avail.
All the research I did backed up what ALJHappyChicken said about the egg not 'travelling the right path' and causing issues. While there are great methods for fixing egg bound girls, I learnt there is nothing really that can be done for 'internal laying' so I really hope that is not what your girls have.
If it helps, Britney's symptoms were lethargy, straining, pale comb, reduced appetite at the start, progressing to no appetite at all, drooped tail and watery poop. She was on a regular worming schedule and two courses of antibiotics. She would have good days and bad days.
I was told that the good and bad days would have been the antibiotics. When she 'internally laid' this would cause infection and the antibiotics would fight the infection but it was a nasty circle, because the next egg would also lay internally, cause an infection etc etc
Apparently, this 'internal laying' more commonly affects those girls who are good layers, like leghorns.
Anyway, as I said, I so very much hope this is not the case for your girls and that this has been a little helpful.
Teila