The obvious things to consider if you haven't done so already are the differences in environmental conditions between the two tanks in order to try and establish whether some aspect is adversely affecting the inactive frogs. Things like water temperature, water quality, filtration, exposure to light, particularly direct sunlight might be influencing their behaviour. I'm not sure what could reasonably described as normal but I think the problem here is that the inconsistent behaviour shown by sibling frogs in two separate tanks points towards something being amiss in the one with the inactive frogs.