hi! 

I posted recently about my 3 girls and how one had gotten sick with a uri and I was asking for advice. I contacted the person I had adopted them from, and was instructed to bring her back for vet care and she gave me a "replacement rat," one of their sisters still there. 

everything was going good, they were all happy and bouncy, getting them used to me was going great, until today.

just to preface: i feed them oxbow young rat food, theres always food around the cage and i put more in daily. fresh water every day, some veggies and fruits on occasion with a mix of pb/baby food and cheerios. i've got them using a dust free paper bedding which i changed two? days ago. the other two have consistently been happy and friendly, very active and bright. 

I hung out with them for a while this morning then took a nap around 2, woke up at 4:30. when I took my nap as i was falling asleep, I was watching them drink water and just do their thing. everything seemed fine. when I woke up, I noticed the "replacement" rat i was given, (not a big fan of the term, nobody could replace penny and i wish i had the option of waiting until after the vet care) she was laying by the door of the cage and I thought she was sleeping. i rushed over immediately because i thought it was weird as hell, said something, then poked her and she didnt move at all. i dont know how she passed away. i've been looking at her body, trying to find what couldve been. did she choke? I found her laying on her side, one of her eyes was grey and her mouth was open but i found no wounds, nothing around her nose, i'm not sure what she couldve choked on, was it a cheerio??? I've been giving my rats cheerios as treats since I owned a few as a kid, i'm just so confused. 

am I doing something wrong?

dont know what i'm doing wrong.