Poor things.
I'm sorry they are not well. If you can get them to rally with vitamin therapy as mentioned. (Direct doses of Vitamin E and B Complex) after a short period of time, then consider their quality of life. A necropsy will hopefully give some answers as to the cause of their decline.
Marek's is still a very good possibility even if vaccinated. The vaccine does not stop the bird from having symptoms or infection, it may help limit the formation of tumors.
