Dying flock

[ChikNLovr]

I just buried my fourth chicken today, from a flock of 9 down to 5. All have died within the last 4 months.
Half of these hens were 3 years old, and half were 2 years old. Mixed breeds: RIR, Golden Sex Link, Speckled Sussex
They have all exhibited similar symptoms:
Stop laying
Looking pale/sickly
Poopy butts, likely from runny poop, but no blood
Lethargic
Dropping dead, usually within a week of initial symptoms.

From reading other posts, I self-diagnosed this as possible coccidiosis outbreak, so I ran to the Feed store and got the balance of the flock started on Corid today. But my research implies that cocci typically affects younger chicks, so I'm not 100% confident in this diagnosis.
After the first death, I scrubbed out the coop(s), and inspected the girls for insects. I also ran them through a course of de-worming, even though I saw nothing in the feces with my naked eye.

I was preparing to add to my flock, but I certainly don't want to bring any chicks into this mess.

Any thoughts or suggestions on what else might be going on? Thanks.

 

[Isaac 0]

Certainly could be cocci just because they don't have blood in there poop doesn't mean they don't have it you could try using the corid it wouldn't hurt