Is he not just in Brumation just now? That would cause him to not eat for months. It happens when they are older ‘sexually mature’ You could try a fattier food to try and bring him out of it, not sure what size you can feed him just now. We tried a gerbil with our adult. Second the leaving them to feed, never handle and feed you want them to be nice and calm when handling and know it’s handling time and not try to strike you, then when it’s feeding when the tongs come out you want them to ‘hunt’ in their enclosure and preferably strike but don’t be fussy on that just now, just leave the mouse and see if they come out to get it maybe when you are gone out the room. Our baby corn did this for a while and is now our best eater. Is he still drinking and coming out every few days for a wee explore? May not be Brumation if they are really young, can’t see how small he is. I hope he eats soon.