Losing Chickens, Not Sure Why?

[Dreamchasers5]

We are still fairly new to chicken keeping and I am rushing off to work...we have just lost our 3rd chicken this month. Simply just died overnight in the coop...bodies unmarked, now mites found, very deflated. The first 2 were our big beautiful orpingtons....this morning our naked frizzle. What could be causing this? What should I look for? They showed no signs of being unwell....
Many thanks.

 

[Miss Lydia]

We are still fairly new to chicken keeping and I am rushing off to work...we have just lost our 3rd chicken this month. Simply just died overnight in the coop...bodies unmarked, now mites found, very deflated. The first 2 were our big beautiful orpingtons....this morning our naked frizzle. What could be causing this? What should I look for? They showed no signs of being unwell....
Many thanks.

I think if you post here https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures you may get more help.