watery hen eggs

Hi ppl, just wondered if any1 has any info on hen eggs. I recently purchased some battery hens and when cracking open their eggs ive noticed its like a normal egg but with a watery substance around it, but quite a lot of it. Any ideas on what it could be??? Any advice appreciated.

Thanks for the reply Grannie Annie, but are you sure its because they are getting old? I have saved battery hens before Grannie and never seen this. I also have some 5 year old light sussex and their eggs are still great. Never had any problems with other birds either, my polish are over 2, I have 3 year old mixed banties and still never encounted this problem. Another thing, the farms get rid of these birds at around 9 months old, they would of been laying for the last 4 or 5 constantly, so the most I would say they could be is 1 yr old... Im still not gonna try eating these eggs, will get rid of them for atleast 1 month to be sure that they are only producing eggs from the feed I give them. I have small children and do not want to risk anything. Thanks for the advice though Grannie, have a good day...