Broody is committing Filicide!!

[tacothechicken]

Alright so around two or so weeks back, I had a broody lose 2 24 hr old chicks to a freak snowstorm. She seemed totally in denial and was stuck in moody mode and proceeded to act like she still had those deceased chicks, so i allowed her in our shop were we had 2 batches of brooding chicks. She took all 13 like it was nothing! Unfortunately we had a delayed hatch around 4 days ago and knowing she had so many babies i thought she'd be ok. So in went 3 more chicks! ... 7 hrs later the single solid brown chick was dead, looking like it had been smothered and then she had picked at it to get it up. I brushed it off as a unfortunate accident and left her to croon over her babies. Last night I separated the 6 smallest chicks into their own brooder above the hen and older chicks as I feared the smaller may get trampled amongst 13 or so larger chicks. The hen seemed alarmed but didnt appear to care after the chicks quieted down and went back to calling the bigger babies over for feed and water. This morning I came out to 3 dead 3 week old chicks. She had to have killed them all 3 killed chicks were dark breed birds aka a welsummer and 2 ancona I wanted for eggs :"( every other chick was white or biege buff orp, Delaware, etc. The chicks we're long dead and had had the fluff skinned off their backs. Obviously I was horrified and immediately threw her outside whith the flock, only to find...she was fine. No need to run back to the chicks, no growling etc. Totally doesn't care!!!
What triggered her coming out of being broody? And why was she selective in killing chicks she's raised dark feathered chicks before, but the deceased clutch was a pair of blond babies..? All the chicks killed had listened to her just as perfectly as their lighter siblings, and I dont think i will ever allow her chicks again until ive figured out what happend. Did me separating the younger chicks just helped her recollect that her own actual brood was dead? But she originally growled and acted broody when I separated her from the bigger babies ? Any one have any insight?
This was her whith a now deceased chick only a few days ago

 

[aart]

Had she ever brooded and raised a batch before?
Wondering if she didn't also kill the 2 she hatched.
Some birds just aren't good mamas.

 

[tacothechicken]

@aart yes she has, and raised those ones perfectly fine, all chicks grew up perfectly healthy and no issues her 'son' from her last clutch is our current rooster and just scared off a hawk moments ago when it was eyeing my pigeons. I also underestimated her apparently. It's not that shes not still broody, she just knows me well -_- she seems to know ive purposefully removed her from the chicks and that the only way to get back to them is through me. She's wandering about chirping and running up to me every few minutes to let her back inside the building where the chicks are. I removed one chick and placed it a few yards from her to test it out. She immediately called it over attacked any curious hens and then sat on the baby like nothing was wrong :/ when I removed the baby she accepted it, but them came up and walked between my feet waiting for me to pick her up and take her to the chicks again :/ I'm planning to leave her whith the flock today and tommorrow let her see the chicks again to test how brood she really is, and cause I don't want anymore deaths. She certainly knows I'm the one choosing when she gets to spend time whith the babies though. She met my 5 week pullets for the first time and I noticed that while the Delaware and white Americauna had no troubles around her, when our barred pullet ran up she raised her neck and tried to peck it, the Delaware chick was very put out and was fully ready to defend her flock mate, to Pennys confusion at being neck flared by a 5 week old pipsqueak she'd never met lol.
Could she have somehow got it in her head certain colored chicks were from other hens? Non of our other 8 girls are broody so she has no reason to think any of the chicks are from another hens clutch and ive never heard of a hen unwilling to raise chicks hatched from other hens eggs :/
Here's her and a baby I placed in front of her post putting back outside including her sitting on it in the chilly morning air, and there's her previous baby, our EE rooster standing guard outside a nestbox while his favorite hen lays.

 

[chickens really]

Could a Rat have gotten into the Brooder? Strange she killed them after raising them. Possibly she is weaning them early too. I had a Hen that weaned at 3 weeks old.

 

[tacothechicken]

@chickens really there is that possibility but we haven't had any signs of rats in our shop since last summer since we moved our cats into it,(no cats werent in shop at time of chick death) plus we had a starving family of rats kill and eat a pigeon a week or two back on a back acre of our property, but these chicks weren't eaten, just killed,(our rats are big enough they would've been able to kill a chick and carry the chick off too, but they wouldn't waste time killing 3 babies and not even taking one whith them as gruesome as it is) and I am positive if the rat had time to kill 3 chicks, penny wouldve had time to kill the rat...and no rat bodies have been found :/ either way Penny has been reintroduced now to the flock, and while not laying again yet, she is no longer broody and watches her adoptee chicks in their pen from a distance now accepting her lack of motherhood this season, I don't think she'll go broody a secound time, she's a Banty so it takes a lot of her energy, and I think she's content whith playing aunty for now. Although I do plan to put our 5 pullets and 8 cayuga +1 Swedish ducklings in the main coop tonight, so we'll see how that goes....