Hi, My Baby Is 1 1 Months Old And She

Hi, my baby is 1 1 months old and she had these dark circles under her eyes. It comes and goes but sometimes it's pretty dark. And she had for a few months already. The doctor run a blood test to see if it could be anemia but everything came out normal. She sleeps fine, she eats fine, her development is great, and she doesn't have trouble breathing. Also I don't see her scratching her eyes so often. She does tap on her head very often and she is also teething. I wonder what could it be.