Chickens sick or dying, are they just getting old?

[7 chicken army]

My flock is 4 years old this spring. I had one bird I had to euthanize because of ascites about 6 months ago, one bird had internal egg problems about two months ago and had to be euthanized, one bird recently I found dead under the roost and I am assuming it was a liver problem (did a quick look to see), and now today I have another bird that seems to be having fluid accumulation problems and probably will need to be euthanized. Is this just because my flock is getting old? Could it be because I'm feeding 18% protein all the time instead of just at molt? This is my first flock, is this kind of attrition normal at this age? I'm just wondering what the heck is normal and what isn't. Two of the birds (the first one with the ascites and the one that died unexpectedly) were adults when I got them via Craig's List but they seemed quite healthy and better than hatchery birds. The rest of mine are hatchery buff orps. I thought if I got a heritage breed I'd have a healthier bird but now I'm not sure if it really makes any difference.

Please tell me, if you've had a flock a long time, is this normal? And is this about the right age for it? Thanks!

 

[bobbi-j]

Unfortunately, most chickens are not long lived. I don't remember having any past 3-4 years old. (I usually process before then because I want productive layers and not freeloaders, but I have tried to keep some longer without much success.)