Need to understand my chicken behavior

[Tomcoll67]

Last night I put DE on my chickens and in the coop. I noticed flies in the coop so I thought this will help.
TODAY one chicken w as lathargic and having labored breathing. She died 3 hours after I noticed the behavior.

I did give her a bath and checked for nits and mites.
the other chickens seem to be active and unaffected. Did I kill the chicken with the DE?

 

[Ol Grey Mare]

How much, and how, did you apply to each bird and how much was applied to in the coop?

 

[Tomcoll67]

I applied with a pest pistol. 1 squirtingeach side and 2 on floor. 1 squirting per egg laying section. I segregated the chickens from the coop at that time. I also used the pest pistol on the chickens. I sprayed it over the feathers.I gave a quick puff of the pistol for each.

 

[Tomcoll67]

This chicken is also our favorite with the most personality.