Pictures would help here. There is a little icon that says "insert image" when you mouse over it. Click that to upload them.
Food should be no bigger than the space between their eyes. A cricket will definitely bite the frogs. They should be kept on damp, unprinted paper towel as they morph, skip the gravel (always) moss and substrate. Being unsure as to what species they are, I would keep a bowl of water in there no deeper than their chin, and it should be treated with a dechlorinator.