l have lost 3 hens and need help

I had a flock of 23 Hens going into the winter and now am down to 20 with 2 more sick. The symptoms are weight loss (can feel it in their chest) lethargic, and then they get off balance. Once they show symptoms it has taken anywhere from a couple weeks to about 1 week to pass. I figured with the winter, losing a couple wasn't a huge deal, and the 2 i lost were the same sussex breed, but i had 1 come down with very similar symptoms about a week ago and she was getting picked on by the ducks and some of the chickens. I moved her into a safer area but she has continued to get weaker and more off balance. This morning was where the alarm bells went off, i have another hen that started to wobble and tonight she is just sitting in the nesting area where all the others that have died started to go at night.

Im thinking about putting these 2 out of their misery and hoping they don't spread what ever they have. I am planning on totally cleaning out my coops this weekend but would really like some help or any insight as to what may be going around my coop

Thanks so much

That's the exact same symtoms my one hen had but it wasn't spreading and I treated her with corid kept water and food in her by force feeding and drink and she got better but since it is spreading so fast could it be mareks

Did u syringe feed? When u mention force feed. Also how did u administer corid?

O only syringed the corid water in her and u put the corid in the water and I took some of there layer feed and some corid water and just put a little water in her mouth at a time and I'm not sure if this is what ur dealing with since it's spreading so fast have they been vaccinated

Ya it sounds like mareks and since its spreading so fast I am positive that's what it is