I would say one is crashing out right from the start and needs to be 'reset' in windows, then restart the program.

if you have any OC settings applied I would get everything up and stable at stock clocks then start inching them up if that is what you want.

Usually when a card crashes it lowers the settings automatically to keep any damage from happening on that card, but it keeps going at the lowered speeds until it resets.

The other outcome is if it doesn't 'crash', you will see outrageously high numbers streaming on the screen, but the fix is the same either way.

Just go to device manager and disable/enable the card.

Hope that helps.