how long have you had them for? I don't even attempt to feed mine until I've had them for about a week, and if feeding day falls on less than seven days i don't really expect them to take it. It's still important to offer, but don't be alarmed if they refuse even up to five meals (I have one that likes to eat every 3 weeks). As mentioned before; don't boil your rats. I read your post as "I boiled two rat pups for 30 minutes" which I know can't be right, because boiling beef ribs for that long cooks them through, and rat pups at that point wouldn't even be recognizable. I leave my f/t rats to thaw at room temperature, finishing by placing them in lukewarm water just before offering. Also (and I don't think anyone has said this before) I would not move them to a separate tub to be fed. There's some debate around it, but I personally don't even touch my snakes on feeding day or too late the day before. Moving them into a new environment to eat is just too much excitement for a species already known to be finicky eaters. The feeding response isn't something to worry about with balls, and even getting bit doesn't hurt too bad (it bleeds a good deal, but it doesn't really hurt). Rat bites are much more unpleasant, believe me...
Lastly; just relax. If they're hungry they'll eat, and it may take them a while before they decide they want to. From what I understand, it's pretty rare to have a snake starve itself to death as long as you're offering proper food regularly.