What causes runny liquidy egg whites?

[fluffycreatures]

My Friend has chickens and asked me to post a question. She says shepicks all her eggs up everyday and they are usually eaten within a week. Sometimes the egg white is firm and thick when broken into the pan and sometimes it is a liquidy this puddle without the firmness.
She would like to know what conditions lead to runny egg whites?
Thanks
Dianne

 

[eggzettera]

&

Check this out http://www.thepoultrysite.com/publications/1/egg-quality-handbook/30/watery-whites I keep the main site bookmarked http://www.thepoultrysite.com/ourbooks/1/egg-quality-handbook/ for general reference.
HTH
Nadine