Great that two ate!
That said . . . 15 minutes is the amount of time a non-eaten mouse is supposed to stay in the enclosure. Leaving rodents with snakes unattended is VERY UNSAFE for the snake and the reason we already recommended times of 10-15 minutes before the hoppers are removed. So. Remove the uneaten mice, set them up with mouse food and water. In a week, either re-offer the uneaten mice to the two babies that have not eaten, or give them to the two babies that have eaten. Then, when you, remember to stick with the 15 minute max rule.
But, hey, two babies that have eaten is a start.