X 2 John nailed it perfectly adult are more prone to go off feed when changing environment and at their age and weight it is not something I would be concerned about.
If they were live feeder feed them live (I would also suggest smaller preys, they don't really need a large rat) than once they start eating for you you can try to convert them.
Just keep in mind your priority is to get them to eat for you, switching is secondary.
Also keep in mind switching animal that size to F/T can take months so if you intend on breeding them this coming season you might want to re-think that and wait until after they bred and lay eggs, at that time it should be fairly easy.