Has anyone experienced their pregnant female coat color changing?

I bred one of mine 4 weeks ago, but I noticed 2 weeks ago that he coat around the shoulders and rump were getting significantly lighter. She is normally a darker shade of chocolate, and now those areas have turned light brown/dark tan almost. I am not 100% sure she is pregnant. Her nipples have dropped a bit and are larger than I could claim to be normal.

Got her on a raw diet, supplementing with Bitch Pills. Haven't included any oils and wondering if that could be the reason for the drastic coat change in those areas.

Just wanted to hear about some experiences. Thanks!