All seems to be ok, would you please post a pic of the enclosure and clear pic of the frog. Would you please describe how are you feeding them. I'm asking about the ones that are not eating.
To clarify: you have 9 frogs. 5 are eating, 4 are not? Everybody are in separate enclosure, right? Are you asking about only one that is getting thin and questionare you responded is about that guy?