Baby diarrhea but doctor not worried?

Ella

My daughter's had diarrhea for a week now. I don't mean constant over and over, it's just when she poops once a day it's just liquid. He asked if it was loose or watery, I said watery, he asked if she's been sick. She was sick two weeks ago with a cold but that's been gone. No fever no cold, nothing now. He asked if she's been eating normal and I said yes. She about to be 5 months old in two days. She drinks 4oz every three hours and is 20lbs and 27inches long. She's already the size of a one year old, she's not obese. She's legit just a big baby. Her father is 6ft tall and she doesnt even drink that much. She's completely healthy and doc didn't see anything wrong with her so he didn't seem concerned at all.

My mom guessed that because shes grown at such a fast rate that she just needs to start solids since she thinks the milk is just going right through her but idk. Nothing wrong with the milk, she's been drinking it and it's never done anything wrong to her, she drinks similac. doctor said she's fine since she's not sick and she eat as usually and nothing looks wrong with her