Chick had seizure followed by death

[BrazilianChick]

This morning she was playing around, eating and drinking, she was just fine, but in the afternoon she started getting lethargic, couldn't keep her eyes opened and couldn't stand up for a long time and now by night these symptoms got worse so I picked her up to check for anything physical like broken bones or something like that, then I realised that she wouldn't make it so I stayed with her till she started kicking and bending her neck like crazy until she calmed down and stopped breathing and passed away in my hands. She was 5 days old and so far is the only one who died like this.
So I'm dead inside right now and I just wanted to know if anyone knows any diseases that could've caused her death and if I should worry about the other chicks.

 

[Rose Quartz]

This morning she was playing around, eating and drinking, she was just fine, but in the afternoon she started getting lethargic, couldn't keep her eyes opened and couldn't stand up for a long time and now by night these symptoms got worse so I picked her up to check for anything physical like broken bones or something like that, then I realised that she wouldn't make it so I stayed with her till she started kicking and bending her neck like crazy until she calmed down and stopped breathing and passed away in my hands. She was 5 days old and so far is the only one who died like this.
So I'm dead inside right now and I just wanted to know if anyone knows any diseases that could've caused her death and if I should worry about the other chicks.

What breed was she?

The seizure you saw likely was he throes of death and not really a symptom.

 

[BrazilianChick]

What breed was she?

The seizure you saw likely was he throes of death and not really a symptom.

She was an Índia gigante or in english "giant indian", I've also noticed a LOT of translucent slime inside her mouth.