Hey Paul:
Any drop in water temp in late summer or early fall seems to improve their appetite and bring them shallower here but when it falls from the mid 70s to around 60 they seem to be the most ambitious. When the temps fall much below 60 they start to move deeper again and get less and less aggressive.
It's pretty much the reverse of the pre-spawn/spawn/post spawn pattern.
We did a little scouting this morning in between building bambo crappie condos and found some as shallow as 6-feet in 10-feet of water and they were willing to nip a jig fairly well. The surface temperature was just under 80-degees - down from the upper 80s about a week ago.