Well, if you are getting a mold/fungal buildup then it is likely that your humidity is too high. I would recommend that you clean your habitat entirely -- change the substrate, change the water ... everything. This should be done every two weeks anyway. At least twice a week you should spot clean ... never let old food stay in the cage after your toads have stopped eating.
That should take care of the smell ... regular maintenence should keep it from coming back.
It is probable that you have a dead fish or something buried in the water somewhere ... lord knows that would explain the smell!
You also mentioned something about a cricket tub. If you keep crickets then it is also necessary to provide regular maintenence for them, too. Cricket enclosures should be cleaned out entirely every week ... otherwise they stink BAD. This is also necessary for the health of your frogs ... remember that they have to ingest that stuff!!