yea there was a dead frog in the tank last time i got my most recent frog from petsmart. Dont know if it was directly their fault, im there pretty often for crikets and they always seem well kept + fed so idk what happened. Theyr only a dollar? Theyr about $7 at petsmart around here, i prefer them over Petco tho. Earthworms should be ok although i wouldnt recomend getting them from the wild because, as youve heard, they could possibly have absorbed pesticide or other things that could be harmful to your frogs but thats a decision you'll have to make. Waxworms are good too but only as a treat once in a while because of their high fat content. Are you feeding them stricly worms?