I have a similar problem with one of three BR pullets (10 months old), that stated laying last October and free range daily. The first pullet to start laying had blood smears on the shell. The shell wasn't wet or covered in blood, just some smears. She continued laying such eggs for a few weeks, then stopped altogether. She hasn't laid an egg since early December. The other two pullets consistently lay every day or close to it. I've maintained 16 hours of light daily, and all pullets get the same laying mash (and appropriate treats) and seem quite healthy.
Will the non-laying pullet ever lay again? Is that even possible? She's not even an official "hen" yet!
Any suggestions are appreciated.
Pay closer attention to the hen that isn't laying. What lots of folks do with layers that slow down when they should be producing, is give them an injection of A&D vitamin to prevent calcium deficiency. What you are experiencing isn't outside the norm. Rapid change in weather, long periods of cold weather with little sun causes egg production to halt. Sunlight stimulates a photo receptive gland near the eye of the bird which causes the release of an egg cell from the hen's ovary. I don't believe artificial light can do what the sun can.
Anyhow, I don't want to get off subject too much in regard to supplementation. Make sure the birds have oyster shell. I gauge how much they need by what is left in the feeders. I mix mine in food since I've had a few dumb hens fill their crops up with oyster shell in the past and get crop bound. Use a good quality layer pellet and boost up the protein level by mixing in some grower crumbles. I don't understand the tendency of layer rations to be around 16% protein when 20+% is better. You can either use a good water dispersible vitamin powder like Broiler Max or Avian Super Pack, or you can supplement the feed with something like Red Cell or Poultry Cell @ 1Tablespoon per pound of feed. Mix it up good in a bucket so all the feed is coated, and give them just enough so they will eat all of it. I've tried these methods in the past and they've seemed to help. Then there are hens who are just poor layers due to genetics or some disease. I guessed you would have mentioned some symptoms if you thought your hen had any diseases.