4
questions:
1) what kind of live plants are you using? Some can be toxic
2) is he solely eating crickets?
3) is there a background around 3 sides of the tank? Sometimes stress can cause the frogs to flip and if the enclosure is in a high traffic area, that may be the cause. A background will keep him feeling secure
4) are you mixing the vitamins and calcium together? The only supplement I know of that's formulated for this is Repashy Calcium Plus. Otherwise, the calcium can prevent from vitamins and minerals from vein absorbed properly, and vise versa. Try using the vitamins once a week and the calcium every other feeding, and not at the same time!

Lynn is right, Grif should be able to help further!