Check out a condition known as Short Tongue Syndrome (STS). It is related to a low Vitamin A retinol level in anurans. It's more prevalent in toads, but the symptoms you described sound like this, ie, following the food item, trying to apprehend it and missing. Double check your vitamin supplement. With dart frogs, I tend to use a multivitamin once a week and use calcium every other feeding.

Good luck with the little guy.