I have one suggestion, it look like you are keeping them on sand... I would switch them to something other than that. Try aspen shavings, carefresh, or even paper toweling or newspaper work great!

I would just mince up the fish really fine, but don't use minnows, they contain thiaminase like goldfish and are toxic over time to your snake. You can use feeder guppies, but you have to make sure that they are indeed guppies. You can also use salmon, trout, or tilapia from the supermarket. once you get the babies to eat some fish, start cutting up a pinkie in with the fish and mix it up well so all they smell is fish... gradually change it over to just pinkies, and it should work for most of them!

Good luck!