Get rid of the RO water and use the treated tap water instead.
Try offering some nightcrawler pieces. At that size, we offer food nightly. Try offering food in a separate container, they can learn a schedule and get "Trained" to tong feeding & the change in location for feedings. The enclosure may also be a factor.......the smaller frogs need a smaller area and can be intimidated by large open spaces. If you do try the worms, make sure the pieces are no bigger them the length of the frog itself. You can take a look at our videos for tips on feeding if you'd like, we made them specifically to help others with tong feeding.
Ivory Reptiles - YouTube
Best of Luck!!