Gosh Krista, Your breeds are so hard to come by.
Darn those cockerals! I had a bachelor pad last year, 4 blue JG's, and a BO. Worked out great, as long as no one went out and came back in. I would have held on to them, but I had a blue Orp pullet die, then a while later, a splash JG roo died, and I then dismantled the bachelor pad.
In my silkie coop I started with 2 roos and a hen that I hatched here. They were fine, and 3,5 years old. I had added a white silkie pullet that was at a swap. A few months later, my silkie roo died with Marek symptoms. 3 months or so later, the white silkie died-wasted away. Since then, the silkies have had 2 hatches with no deaths. So I imagine that the hatched silkie chicks are all somewhat resistant to Marek's. Now they had hatched those 10 Polish eggs that were mailed to me, and 5 have died or have symptoms.
It appears that my silkies' eggs/chicks are born with resistance. I wonder if the other older chickens would be laying resistant eggs? Of course they'd be resistant to the strains here, but I don't know about elsewhere.
(And I tried not to mention that my silkies have only had girls, no boys, and I have them all, none were given away.)