if it is a baby i would feed every week. misting the substrate 1x a day works well for humidity, esp make sure the substrate in the hide box gets a good mist. substrate should be 100% dry by the afternoon/evening.
feeding can be tricky. when small i would feed mine, wait till the 'bulge' in their belly was gone, wait 2 more days then feed again. this may start as 1x per week then advance to 2x per week as they get bigger. after 2-3 weekd of 2x a week feeding it's time to move up to the next larger size mouse.
HTH and that is what I did with success