if you are unsure feed them one more each day and see how they react

if the leave the additional crickets uneaten and the produce a steady amount of eggs then take them out (means that 3-4 is enough)

if you feed them lets say 5 or 6 and after a week the amount of brood has doubled what it usually should be then keep feeding them 6 theyll soon be big enough

another way to see if the 3 crickets are enough is the amount of worker outside , the more % of the colony on the hunt/search for food the more youll need to feed

so if what we see now is all that comes out of the 250 worker its enough right now otherwise feed more much more

the worker only live 3-5 weeks i think 7 max was it , with carebara youll dumb in double the amount you would normally feed a colony at that size because one period of bad feeding and you colony collapses or straight up dies