eggs

I have three birds & in the last couple of days have found that perhaps one of them has started breaking and eating the contents of a laid egg.  Is this usual behaveour and is there any advice how to stop it. 

I wonder if they are laying thin shelled eggs that have broken and they are eating them to remove any evidence.

Im getting a broken egg daily at the minute. Mine are partially moulting which is what i think is causing the thinner shells (its only affecting 1), that comnined with all the jostling in the nest box its little wonder we get a broken one.
Sometimes they will eat it straight away and sometimes if i see its cracked i will throw it to them. They dont eat the others though.

I''ve found if i make their layers pellets into a porridge, they eat more that way which improves the shell. Oyster shell and grit is always available but they dont seem to touch it

in which case you may need to either buy or make roll-away nest boxes which will stop the eater from getting to the eggs.