Why did my three African Dwarf Frogs die?

you are over-stocked and adding salt to freshwater fish is wrong ... salt is not required for your betta and even more so detrimental for the frogs ... and the tank is too small ... it is barely enough for your betta and you added three frogs !!! get a bigger tank if you want more fish ... why you even thought that would be appropriate is beyond me ... and nothing in the tank should eat freeze-dried, ESPECIALLY the frogs ...