Sorry for the delay. I went up into our attic, which is directly above the cracks. The area is dry; the eaves above the spot as well as the pink insulation were both dry. (That's the area shown in the closeup picture, just "north" of the recessed light fixture. The difference in color is due to a nearby window. Up close it's all the same).
wonder if poor insulation didn't cause the cracks. As the attached pics show, the insulation in my attic leaves something to be desired. We bought this house after a renovation, including a new roof. However, it appears that new insulation was not part of the renovation. Perhaps the difference in temperatures between a chilly attic and a nice, warm house led to expansion cracking? The cracks are right next to some recessed ceiling light, perhaps also leading to some heating of the surrounding ceiling?
I'd appreciate any thoughts as to:
(1) my theory;
(2) how I can/should fix the cracks;
(3) whether/how I should upgrade our insulation.
Again --many thanks to all for your help!