Thanks for your query.
Your child is having fever for last 2 days initially on higher and now came down along with lethargy,these are features of viral illness and take few days to settle.
,since due to illness she is not taking adequate diet so she is not passing adequate stools.
I suggest you to give her acetaminophen
if fever is more than 100F,
Give plenty of fluids,coconut water,glucose water,vegetable soup and simple soft diet
in small amount so as to maintain hydration and nutrition.
In case symptoms continue get her evaluated by pediatrician
Wishing your child good health.