One of my hens died this morning and I don't know why. I had three hens; a speckledy, a black rock and a bluebell. I got them at 16 weeks old and all three had just started laying. Now at 28 weeks I found the speckledy dead in the co-op. The remaining two hens seem happy enough although the black rock appears to be sneezing. Can anyone advise on why she died? Should I consult a vet?