Hatchling feeding question

One of my hatchlings is only 45 grams and i have offered him a hopper mouse twice. He is not my only hatchling that has not eaten but he is the smallest. He hatched around may 4th 2013 so how long should i wait before assist feeding him. I am worried because he is only 45 grams. Thanks

Has he lost weight since hatching? What is he housed in? Substrate? What time of day are you offering? How long are you leaving the hopper in with him?

Normally after theyre all out I wait until the 3rd week