Three days isnt a big deal.
They eat smaller meals less often when they are young, then gradually eat larger portions (worms) less often.
I have also noticed in mine that different stressors and conditions will interupt the regualr pattern.
Before i had a chiller to control temp, i noticed that a few warmer days or cooler days might make them"moody" and not take food.
I have two males, & I've also noticed that they seem to go right off their food before they drop spermatoza - they'll have days of kinda unusual adctivity (a bit more pacing etc than normal) refuse food for days - then hello! I'm left a nice bunch of jelly to clean up
i've also noticed they won't eat before pooping - they'll refuse food on their normal day, then next day, get the turkey baster out!
So there is three examples of when my guys seem to go off food that are totally harmless. They could be totally wrong assumptions, but it's only my theorising from what i've observed.
Being the type of creatures they are, and the cold conditions they live in, they have slower metabolisms than us, and dont have to eat everyday.
Yes, you should be looking for unusual behaviour and eating patterns etc as indicators for a problem, but not eating for only three days is not something to worry about too much.
His torso should be roughly the same width as the width of his head - either narrower or wider than that can indicate over feeding or under feeding respectively - if they decide to only eat once or twice a week, and they hold good weight - you don't have an issue
Bren