I'm very sorry for your frogs death ! Crickets should be same size (or smaller) than the distance between the frog's eyes. Larger ones could cause problems. Night crawlers available at Walmart and bait shops are great food. Will need to cut from pointy end into mouth sized chunks for babies, body length ones for juveniles, and the adults can handle full worms .

What was your enclosure substrate? Anything in there that frog could eat and cause intestinal issues (i.e. sphagnum moss)?