My flock was diagnosed with Marek’s. I’ve lost 2 chickens to it. I tried allll the things, including hypericum (I used St Johns wort capsules but have the plants here as well). Unfortunately for my girls it didn’t work. However the rest of my flock is fine, and we had a hen hatch our current rooster and he’s been fine (unvaccinated) so far. He’s 13 weeks now. I plan to try to breed for resistance like the Amish around me do. Good luck on your journey!! 
