Question Why did my new chickens die?

[Jetsko]

I'm new to raising chickens - here is my story with questions at the bottom. Any advice is gratefully accepted.

Last year we purchased a home that had a secure chicken coop, tiny run (3x6) and three red chickens, species unknown. Which we promptly named Elvis, Priscilla & Presley. From fall to spring of this year, we let the chickens free range most days. In March, a fox had Priscilla for lunch (very sad day for us) and we started to make plans to increase the size of the run and add new chickens. Added a covered 10x10 run that attaches to the old run & coop via a short tunnel.
In early June Lisa & Marie joined the group. I blocked the tunnel, all girls roosted in coop at night, in the morning I move Lisa & Marie to the big run. Left Elvis & Presley in the old run & coop for the morning. In the first week, only Elvis & Presley free ranged under my supervision, 2nd week on Lisa & Marie joined the old girls in the yard (we have an acre). After free ranging, Elvis & Presley were placed in the new run, Lisa & Marie in the old run & coop. If they had a 2nd free range time, again they were switched as to which run they were in. At night whoever was in the new run was carried into the coop to roost & everything was locked up. After 2 weeks, I unblocked the tunnel and monitored chickens for bullying. Some pecking from old girls to new but no blood or lost feathers. In the run, they have 3 feeding & 2 water stations.
I thought I was doing everything correctly but then at almost 4 weeks, I opened up the coop in the morning to find Marie dead on the floor. No blood or trauma to her body, just dead. Marie was a flyer, who startled easily. There was a wild animal smell around the coop that morning, but no signs of a predator trying to break in. I thought maybe Marie got scared and tried to fly high but hit the roof of the coop then fell to the floor and died But this morning, Lisa was dead on the floor, again no signs of being attacked just dead.

I'm so upset - Did I do something wrong? Is there something I should have done but didn't? Anyone have any advice for me?

[kenya]

Were the chickens coughing at all?

[Killerbunny]

Is there plenty of ventilation in the coop?
ANyway, welcome even though it's not great circumstances. We'll try to help out with no judgement.
Sorry about your lost chickens.

[Jetsko]

thanks for responses

The young chickens didn't show any signs of illness. Eating, drinking, pooping, dust bathing just like the older girls.

As to the coop, there are 3 vents near the top of the walls, I recently used the shop vac to clean the vents to ensure that they have proper air flow

Coop sits on a cement pad, siding for walls, metal roof & soffits. I've checked the perimeter for signs of digging or scratching and everything looks solid.

[ross]

Ex venting fresh cooler air in , stale warmer moist dirty air out . Hot air rises . Luck

[TomK]

Good morning...thats sad about the two newer birds dying as they did..you will never know unless you invest in a necropsy..and most of us dont have that skill set...it being only the newer birds would make me think a common link between them as no predator issue...sounds like you have the coop issue covered ok but as Ross noted, make sure the ventilation is done right, especially on these really warm days...having said all that, Welcome..

[labradors]

Welcome to PTO :).

So sorry about the loss of Lisa and Marie. Where did they come from?

Linda

[Kbr42]

Welcome !

They could have be it's too had in the coop at night young birds haven't figured out the heat yet and they aren't fully feathered, which keeps them both cool and hot. Where did you get the birds from how old when you got them?

[KimChick]

Welcome to PTO! I'm finding that chickens are both robust and delicate.
This is our 4th season with chickens. Our first experience with a sudden death was because of bumblefoot. I had not noticed a hen limping, and if she did, it was not enough for me to take notice. Since then, I have magnet swept for old nails, etc. And I still find shards of glass here and there.
"Here and there" not only means in the chicken enclosure, it means all over the property.

[Jetsko]

In response to recent questions. New girls were fully feathered and started laying eggs the 2nd weeek that I had them.

As ro heat in the coop. Its really a custom built storage shed with a chicken door at one end. At the other there is a human sizes wood door that I prop open because there is a second wall & door made of hardware cloth. Which keep them in & safe during the day. There is a peek bent at the top of the roof as well as wall vents up high and a window that opens with a screen over it.

Coop was built 3 years ago with heat waves on summer and no loss of hens