How much dust are you putting on the crickets? They breathe through their skin/exoskeleton, simply put (it's a little more complex than that), and so when they get heavily dusted they can't breathe. Naturally, when they can't breathe, they can't move, so they look like they've died.

Try dusting them with less calcium. In addition, while gutloading is excellent, and variety of diet is great, it does not necessarily cover all nutritional bases. If you are feeding a truly varied diet with gutloaded insects, then I would still dust, but only once every other or every 3rd feeding of insects. With the crickets, you are also dusting them with calcium to help balance out the excess of phosphorous that makes up their exoskeleton. A light dusting of calcium with D3 essentially balances out the calcium that would otherwise be leeched out of the frog's system to bind with the phosphorous.

As far as not feeding, it is likely a combination of being treated for the eye issue (a stressful event) and being in a strange place. Once he heals up and is back in his normal environment, his appetite should return.

-Jen