what might I be doing wrong, chickens losing weight and pecking

[embrown]

I have 3 BR's and 3 Isa Browns about 10 months old. 2 months ago I noticed that the BR's were getting pecked as they lost feathers near the tale, but not the Isa's. Now some of the Isa's are also losing feathers, none laying around so I am assuming they are being plucked out and eaten. Now I notice that 1 Br is very, very thin, one Isa is quite thin. I checked for mites and see no signs on birds with flashlight at night, no bugs under purch area, no specks on eggs, no bugs crawling on us when cleaning nest boxes or coop. I just brought the tiny BR inside a few days ago and she eats all day, I am giving her layer crumble, water with vitamins, and a scrambled egg every day. Her poo is normal with the exception of two that looked like human vomet. Her keel bone is protruding, and there is not any "bell" rounding at the bottom, and she has stopped laying altogether. Her comb was pale and starting to look shriveled, but that has improved while inside. We are feeding the whole flock Layena layer crumble, they get grit, shell, and lots of fresh water with vitamins and once per weekOACV. I ocassionally give them yogurt, sour cream, cottage cheese as a treat. But, I also think all my birds are "too" small. BR's, according to my research should weigh 7+ LBs but my largest one is just over 4 LBS, and the one I brought in is only just over 2 LBs. I can feel all her bones. My Isa's are all around 4 LBs and they too should be over 6.5 lbs, and the lightest one is under 3 LBS. I feel like I am letting them down but can not figure out what else to do. I have read weeks worth of feeding posts. I have read that mites can zap weight but I do not see any. I have read about worms but do not know how to know if they have that problem or what to do. I used to get 6 eggs most days but now I am lucky to get 4, today I only got 3. I am worried, and want to boost up all their weight, rule out what problems might be causing the pecking, the weight loss, and the lack of overall growth. They are inside a coop kept at 32 to 40 degrees it has several inches of pine nuggets on the floor, and is 4 x 6 floor space coop with elevated purches and nesting boxes with a window and a door to get in fresh air. They have all day access to an outside "porch" with wire floor that is 8 x 2.5 and we just added a way for them to get to an 8 x 3 wire fenced area if they want to peck around at the frozen and snowy ground...which they mostly do not. Is it a feeding problem? is it worms? Am I missing a parasite I should know about, is it a pecking order issue and that is why the pecking, wounds, and loss of feathers that is preventing the two little ones from getting food? Where do I go from here? Any direction would be appreciated.

Worried in Williamston,

Beth