Hello and welcome to FF

! There are many possibilities in here. Was water treated with dechlorinator?
A too dry substrate is bad for froglets. As Amy stated, they should be kept for first 4 weeks in daily changed damp unprinted paper towels as substrate. Gravel is no good for frogs; if eaten it can lead to impaction.
How big was cricket and what is froglet snout to vent length? Too big a cricket can harm the frogs by actually biting them, specially if left in enclosure and it gets hungry. Insects should be no bigger than distance between froglets eyes, gut loaded, and removed from enclosure if not eaten in couple hours or overnight.