Piggies can’t be truly toilet trained. They will go to the toilet where they eat but they will do it wherever they feel like it.
Sorry to be clear, you say puppy pads and newspaper and fleece in the houses - do you mean that the fleece is only in their houses and the the rest of the cage is just puppy pads and newspaper? If so, then that isn’t going to keep them away from the damp, you’ll want a more forgiving bedding than newspaper all over
Perhaps try using some pee pads in their houses as you can then change them out more frequently to ensure they are always dry
If they are long haired, then keep their hair short around their bums