Ok, so this bas been going on for a bit and I "think" its normal because both of my mini-rex's get this....but I'm at a loss as to why. When I rub their cheeks (face cheeks

) (which they looooooooooove

) I can sometimes feel these little hard chunks in their fur. When I look at them closer, I noticed that they are clumps of hair, but it looks like the folicle is growing out with it. Sometimes the little hard part is green and sometimes its brown. They usually work themselves out at some point, then the clump just comes out together. What is this?? Is it normal??