There are a few things here if not done already
Have aspen bedding if you have aspen switch to coco chips
Temps no higher that 88
Continue offering live mice
Add crumble newspaper in the tub if security is an issue.
Now those are the thing that can be done however thisis what is alarming, hopefully any animal that has regurgitated you have waited 2 weeks before offering again?live hopper but a few have regurgitated
Some young animals it's rare but it happens with either not eat or regurge when they do even when kept in optimum environment, those are usually animals that have some type of gastrointestinal issue (malformation blockage etc). Prognostic on animals with this type of issues are usually grimm as not vet would nor would likely be able to perform any type of surgery to correct the issue (if that would even be possible) on something that small. I had a few over the years it's sad but it's one of those "not meant to be" so you need to be aware of that possibility.
Now those animals even if unlikely at that age could internal parasites, that however is treatable.
There are also animals that fail to thrive and will never have the willpower to feed on their own.
The last thing if everything fails will be assisting depending on their overall shape and see how that goes and see if they keep the food down, if they do, assisting for a few meals (always alternating by offering live first and assisting next day if refused) may trigger them to eat on their own but right now not keeping the food down is more concerning than not feeding.