change color?

[bgdawgrr]

I found this rather interesting. I saw two of my girls' litter mates pictures at work when I brought my girl in and we swapped dog stories. It tripped me out that the others had "changed" colors to almost all tan with just a little black. My girl is perfectly marked, and all the pups looked very nicely marked when we got them. (three of us got pups the same day, same litter. I got the only girl, my workmates picked males).
Have you ever herd of this before? I joked with them that their dogs had "tailtananitis" as my girl is the only one of the trio with the tail docked. I blamed the color change on the full tail. ;)
Anyone know a real reason this may have happened? A well marked dog changing?

[Anne]

Did you buy from a registered breeder? are these dogs Rottie cross? Have never heard of a pure bred changing color like this.