Everything I have read says you should put mealworms in a small bowl so they can't escape and burrow into the substrate. I would say you need to seek them out and remove them. The dead crickets need to be removed as well. Frogs need to see movement in order for their feeding instincts to kick in. One way to keep crickets out of the water bowl is to make sure the sides are elevated above the substrate, other than that you could also offer crickets in a bowl deep enough they can't escape from and burry it in the substrate so the lip is even with the top of the ground. Other than that crickets are very suicidal and any deaths should not be a shock, just remove them from the enclosure to help keep it clean. If you have Sprintails or isopds in the terrarium you can leave dead feeders and the little janitors will come by and clean them up for you. Along with any frog poop or mold.