I've created multiple custom reports. On several of them, the results are a blank, white screen; no results and no errors. Any idea what might be causing this? I checked my site logs, but there are no errors (that I can find). Other than that, I don't know where to start.
Blank pages indicate that PHP has exited ("fatal error" etc), but that debug output is disabled. Your next step is either to enable display of debug in the page output, OR to obtain the debug from the backend.
Please refer to this answer which explains how to debug when you run into a blank page:
Can you be specific about which site logs you've checked? It may be there are some other logfiles you need to look at (see linked answer).