We seem to be getting an increasing amount of spots in eggs. Dark red spots; from what I've read, they are tissue. Our hens are 10 months old. Barred Rocks. They started laying right around 20 weeks and we would occasionally get an egg with a spot. But now I would say 25% to 30% of our eggs have spots. We've been giving them an extra 2 hours of light in the morning. Extra light, but not a full 14 hours. It's been a very cold winter here in Michigan. We heat the hen house, but there have been a few times that the hen house has gotten into the 20's on very cold nights. We've decided to try turning off the extra morning lighting starting tonight. Could we be stressing them to lay too much in this cold? Has anyone had a similar experience? Any ideas? We been selling/giving eggs to friends and relatives, but I'm worried about that now that we are getting an increase in spots. I don't want to get a bad reputation for poor quality eggs. Any ideas to solve this problem would be greatly appreciated.
Here's a recent thread on the same topic, an explination and possible "cure" is given. https://www.backyardchickens.com/forum/viewtopic.php?id=35302
Here's a good link (scroll down to `albumen quality'). Paper is a pretty good primer, overall. http://edis.ifas.ufl.edu/PS020