The Curse of Cannibalism, Galus Galus Domesticus Style

I got home from work today and went out back to see the chickens, water the vegetable starts, feed the bees and collect the eggs.  When I opened up the nest box I was horrifically surprised to find two of the seven eggs pecked into.  The golden yolk was still inside and all of the egg white, but a small portion of the shell had been pecked out.  Everything I have read when it comes to chickens going to way of the Donner Party, in a way, is that it is usually a sign of a vitamin deficiency.  Also, one of our chickens gets into our compost piles and Taylor said he saw her eating some egg shells, another big no-no.  I feel responsible for not creating some sort of cover for the compost, which Taylor will be making this weekend.  I am pretty sure the culprit is Sweet Pea.  Her behavior has been getting more and more aggressive when it comes to food and scratch.  She's not mean aggressive, just passionately persistent.  We checked all the birds individually to see if we could detect any "yolky" signs around their beaks, but we found no signs of foul play, no pun intended.  When we checked Sweet Pea, we found a growth of some sorts on her breast.  Neither one of us are a veterinarian, but she has a mass on one side that is not on the other, and that can't be good.  We are going to wait it out, as I am off to San Diego for the weekend.  If the egg defiling continues, we are going to quarantine Sweet Pea and see if we can administer some behavioral reprogramming, you know, shock therapy, water torture, that sort of thing.  Just kidding of course.  Taylor is reading everything about this behavior right now and we will come up with a plan when I get back.  If you are reading this and have experienced this, please leave a comment on what you suggest.