It's crucial to wait until the necropsy results come back so you know exactly what virus you're dealing with.
Marek's and LL are almost identical in symptoms and contagion, but one has a vaccination and the other does not. One exists almost indefinitely in the soil, no matter how much you try to santitize, while the other is very short lived in the environment and can be easily sanitized.
If you jump the gun and get more chickens, even if you get ones vaccinated against Marek's and it turns out you are dealing with lymphotic leucosis, the new hens will contract it because Marek's vaccination does no good against it.
Marek's and LL are almost identical in symptoms and contagion, but one has a vaccination and the other does not. One exists almost indefinitely in the soil, no matter how much you try to santitize, while the other is very short lived in the environment and can be easily sanitized.
If you jump the gun and get more chickens, even if you get ones vaccinated against Marek's and it turns out you are dealing with lymphotic leucosis, the new hens will contract it because Marek's vaccination does no good against it.