Out of my six ex-batts three have been giving long term worries.I worry about them all to be frank. Not nail biting breakdown worry, but they're on my mind a lot. Ex Battery hens can be stressfull at the best of times; under these circumstances where there isn't much I can do for the sick, I just have to walk away so to speak.
However they also really undermine the saying that a chicken will show pain only once it is near death. Two have recovered several times from what seemed to me like a very poor state.
Maybe they did not "really" recover and still have an underlying problem, it is impossible for me to tell. Especially when they are having laying difficulties, it seems that they will suddenly start foraging again happily around as if they hadn't been acting like they were dying for a week.