At this age, it is important to feed or at least offer food on a nightly basis. It may take some effort on your part to get them to tong feed, but that's your job as an owner. We feed 200+ a night at times......if I can do it for that many nightly, surely you can make the effort for one. If you tease them with the worm bits.....jiggle them, make the worm do the zombie dance and tickle the mouth with it, their instincts should kick in and walla......eaten worm bit!! They can be trained to feed from the tongs. Once they start to associate the tongs with food, they will get all excited upon seeing the tongs......we have quite a few that attack the tongs no matter what!!

Best of luck to you & the frog. I see that all other advice has been given already and by some great folks.