Were any of them moving at first? Could be tapeworm segments. Also could be another insect that laid eggs on a fresh dropping. Video below of what tapes look like. Kilverm I don't think will help if they are tapes. The Avitrol plus should, the usual med is praziquantel, which it has. I'm not familiar with that wormer, so I don't know what the appropriate dosing would be. Usual recommendation in the US for tapes is Equimax horse paste, or Zimectrin Gold. More info here: https://www.backyardchickens.com/th...rms-under-construction.1220309/#post-19519143
I don't know much about parasites, but it looks to me like those eggs were laid after the poop came out of the chicken. You might keep an eye out for any kind of bugs hanging around fresh chicken poop.