Help with my hedgehog!!?

Matilda, my hedgehog, is abut 3 years old and I have had her almost her entire life. I went to the lake for the weekend and left her plenty of food and water (as i always do), but when i came home and got her out to play something was different. Her little grey fur mask around her eyes was gone!! Her fur is now entirely white! What could have caused this and is it unhealthy? I did change her food recently but I have changed it before and this didnt happen. Please, any info will help!!!