Last week one of my chickens laid an egg that had a little bit of blood on it. Two days later she did it again. The next day she was dead. Yesterday another hen laid a bloody egg and today she was dead. I still have 5 hens left and need some advice before they all die. It was below freezing for 20 days in early January but was warming up when the first hen died. I put a light in with them in December when they quit laying. About 5 days later they slowly started laying again. The low temp at night is now about 24 and the highs are about 43. They are in a 20' x 20' railroad tie coop that has a 4 foot opening all along the front. The opening is about 4' above the ground, and is covered with 1" chicken wire. There are two places they can roost off the floor. They have fresh water daily that is in a heated dog water bowl. They have been eating lay mash and i little pigeon feed. Any ideas on what the problem is?