Chicken laying on its back

[Isabird]

Hello my family has a small mixed flock of 6 bantam hens all around a year old. Two hens began missing lower back feathers a few months ago and a third started to miss these feathers a month or so ago. All three of them have stopped lying and the most recent one appears sickly. She is constantly tired even when she is foraging she falls asleep. She also seems weak. Three times this week when we went to lock the coop we found her laying on her back and she appeared dead. We flipped her over and she was able to go back to roost. Our chickens eat laying feed, table scraps, dried mealworms and they free range in our yard.
I’m praying it is just a parasite thing although I have not seem any parasites. I’m hoping it is not mareks. Anyone ever see a chicken do this? Anyone have any tips or advice? I did order some chicken vitamins and was planning to start adding apple cider ginger tomorrow. I’d appreciate any tips or help. Our chickens have really been a blessing to us in a time of Covid as we eat the eggs and love the entertainment.
Thank you so much

 

[Jessica1981]

The missing feathers and not laying could be attributed to molting. Not sure about the one laying on its back. Perhaps increase their protein intake and make sure they are getting plenty of calcium?