Nothing but trouble with Crimson drivers.. I can't really say that as I skipped 17.4.1 & 17.4.2, but 16.1.1 through 17.3.3 I had an some kind of issue.
I did a clean install of Win10 and installed the latest drivers. The second card doesn't allow me to adjust the voltage/ fans in Wattman. It's grayed out and yes the card is being detected.
Unless the first card is the master and the second card uses the same settings.