A few of my hens crops seem to get large and hard and then soften up only to go back to hard. By large I mean like about the size of a tennis ball. They all eat very well, poop and are active. How do you know if it becomes an issue? I have 14 hens and two young roosters and sometimes it is hard to make sure everyone is eating their share. Some of them may even be considered overweight. Can I give them some cod liver or olive oil as a preventative? I give them a mix scratch thrown on the ground along with a complete layer in feeders and the ground. The nest boxes have hay. We have a large pen and I put down hay in a couple spots that get muddy when it rains. They love to scratch around in this. They also get table scraps and greens daily. Thanks for your input!