Whites tree frogs keep dying

Over the course of a few years I’ve had 8 whites tree frogs, 4 of them still alive. Throughout these years the frogs that have died have all died in the same way (they stop eating, lose weight, belly starts getting red, always laying in water towards the very end), I’ve tried everything including contacting vets/breeders for advice, force feeding, moving them to a different area away from the other frogs, scrubbing there cage and nothing has worked. I’m really just wondering if there’s something I’m doing wrong or if this is just natural. One of my frogs currently is going through the same “death ritual” that all the other ones have and I just can’t stand to see anymore of my babies die like that.