The GIA sent out a laboratory alert today, informing everyone that they have found a new diamond treatment. They currently do not know how it is happening, but they have described the issue as a treatment that temporarily changes the color.
Someone is essentially whitening the diamond (maybe they are using Crest Whitestrips!) , then submit the diamond to the GIA. After some time the color fades again.
Currently diamonds have been submitted by only a few companies, the big offenders are:
L.Y.E DIAMONDS LTD
E.G.S.D DIAMONDS LTD
They have suspended accepting diamonds from these customers, hopefully they can determine the source of this new treatment quickly.
You can view the entire alert here: GIA Laboratory Alert 2015-05-12