What would cause pale eggs?

[driver]

I've got two hens - a Cuckoo Maran and a Golden Sex Link. They both normally lay medium-colored brown eggs. On Tuesday they were brown, and on Wednesday, Thursday and Friday, they have gotten progressively paler each day and they're just sort of tan, almost white. Nothing has changed significantly in the weather, and their food is the same. They were both born in the spring of 2008 and have been laying for a year as of the end of August.

Has anyone seen anything like this before, and what might have caused it? It seems strange that it would happen to two different types of chickens at the same time.

 

[gritsar]

My hens (brahmas) eggs got real pale right before they started molting around the 1st of August.

 

[Imp]

Eggs also may get lighter as the hen ages. My GLW's eggs are almost white now. Started out medium brown. But she is a bit older than yours, about 3 1/2yo.

Imp