First thing stop feeding in a box, this can cause enough stress to lead to a refusal.
Feed in the enclosure, let the prey thaw near the enclosure, simulate a live feeder by holding the feeder behind it's neck dragging it across the enclosure's floor, and of course make sure the prey is warm enough, if uneaten leave the prey overnight some will prefer to feed that way.
BTW hoppers are to small of a food item, hatchling out of the eggs eat hoppers and quickly move to adult mice.
Need to know the weight since you are feeding hopper they must be very small.
Are they house together?
What size enclosure do you provide?
What are your temps? Humidity? How do you measure them? (Type of thermometer and hygrometer used)
How many hides do you have, are they snug and identical?
How often do you handle them?
If they are young they should eat if they do not it is likely 99% husbandry related and fixable.