You can try to feed the frog with larger tweezer's unless he's shy. I'm pretty sure Michie is a boy but I'm definitely no expert at sexing frogs lol. I just remember something about there being pinkish colors under the armpits, like glands or something.
It's difficult to tell because in the last page of pictures it looked like it was just stomach but in these pictures it looks like there is the shape of the ovaries behind the stomach there. Can you get pictures with a light behind the tank and you take a picture from front so basically the light is looking at the camera? You should be able to see sort of through the fish to see if there is any shape of ovaries
Beautiful pictures though! I wish I had gotten as nice of pictures of my little ones as you did of Rain!
And no, she's not sick, that's just marbling ^_^