What do you see when you connect the drives individually? Is the volume just not recognised at all?
Spanned volumes are a real pain when something goes wrong and you run the risk of losing it all by tampering with even one of the drives.
I would recommend firstly taking an image backup of each drive, using a program such as Macrium Reflect. I'm not sure if you'll then be able to re-span them and access it as normal. but at least you'll have a copy you can safely tinker with, without fear of losing all the data.
If the volumes aren't recognised, or are seen as RAW partitions, you'll need to use a data recovery program to get your files back.