toddler always looks tired..?

90% of the time our 2.5 year old always looks so tired. she seems to always have bags under her eyes and dark under-eyes. I never hear her wake up in the night, my boyfriend says he hears her sometimes. And she always has a nap in the afternoon...

maybe she is waking in the night for some reason, but if she is she’s never loud or anything because, like I said, I never hear her make any noise in the night.... or something else could be causing this? my friend said maybe she’s low in iron? 🤷🏻‍♀️