Dead Bird??? Help

[sadieh]

I had hen die about 3 weeks ago who seemed healthy, she was fine that morning and the afternoon was dead. I checked her out and her crop seemed full so I thought maybe she ate something and got impacted. Tonight another dead hen who was fine acting this morning. Also no one has laid eggs in 2 weeks or so at all. I thought maybe the heat but my nephews are laying and others I know of are still laying. No egg shells laying around like the chickens are eating them and I have 2 separate pens, one that has silkies that I'm not getting eggs from either. Any Ideas?? I don't want to loose any more. I wormed with Pyrantel about a month ago a pea size drop per bird, should I try another kind?

 

[Stiggy]

How old were they? Possibly but maybe a different wormer. It could be heat stress or stress in general. Did they ever have darkened combs? like going purple on occasion