Hi,
I didn't understand if the materials are used inside a Layered Material or stacked with Texture Tags and opacity maps, or not at all, but here few ways to do it :
- use a different UVW Tag for each material by placing each one to the right of it's Texture Tag
- use the Projector shader to modify the bitmaps scale inside the material. Caution, it has several issues with some Corona shaders.
- convert the materials Bitmap shaders to Corona Bitmaps and use the UV settings in the Additional Mapping section