Unfortunately, it sure sounds like Marek's to me, but I'm with your boyfriend on this one...you can't be positive until you have a necropsy done. And again, unfortunately, your other two chickens are probably carriers, if not themselves, going to 'come down' with Marek's Disease. I'm so sorry to have to tell you that, but a great number of us here on this site live and have lived with this disease in our midst for quite some time and we're still the same loving and happy owners that we used to be when we first started out with chickens...most of us anyway.
Again, my sympathies on your birds that have passed. And my best wishes for those still alive. There's alot of good info here on this site. And support and comfort too. Stop by anytime.
-kim-