The files pull just fine from one drive, but I can't seem to pull the references from the source file on the second drive.
Exactly what steps have you tried. Please describe in great detail. Please use Lightroom terms like "Import" instead of "pull", which is not clear to me in this context
In the Library module, you should see TWO items with a Green little bar under the Folders section on the left, one for each source drive where the image files were stored.
Click each Folder's name to see where the images are.
You can also press the plus sign by the word Folders and select under "root Folder Display" (the middle section in the drop down menu) and click "Path from Volume" or "Folder and Path" to see where the images in that folder are stored.
If you did Import the photo files from both drives, they should be there when you click the Folder in the Folders menu section.
Hope that helps
Are the drives the same make and model? have you changed the volume name so that they can be distinguished from each other? If you plug both in at the same time, and can not transfer between the two drives, you need to change the volume name.