White nipples??

I know my baby doesn't have a perfect latch my breasts are very large which makes it difficult. But I was comfortable with no nipple pain and baby is a little chunk definitely getting enough milk so I wasn't to concerned. Recently I have noticed one or both nipples are sometimes white when I go to feed her. They are pink after feedings and they are not always white only sometimes. They look almost like a callus or something. Going to check out the breastfeeding clinic this week and see what's up, I'm assuming its her latch. Its not thrush, and they arn't really sore. Anyone experience this before??