Freckles on kittens, should I worry?

When I adopted these kittens in May, I noticed the white one had spots on her nose and inside her mouth. Now that they are roughly 3 1/2 months old, the ones on her nose are kind of growing and connecting. As of today, she has one big spot across the top of her nose and extending down the right side. Is it normal for the spots to change in size with younger animals or is it still a sign of problems like in older cats?