I haven't done this, but the first thing that comes to mind is to make a coriander tea to add to secondary. Take another 1/2 oz of coriander, crack it up, and boil or steep in some water. Add to secondary, then rack on top of that.
My bad. Sorry about that. I'm so used to adding ingredients when I go to secondary that I forgot I was skipping that step for the first time with this wit.
Do you think a half oz would be too much?
She's done fermenting, but the krausen refuses to fall. I heard this was common with wits. It will be hard to mix the spice in the primary if the foam is sitting about a quarter inch on the surface. I might have no choice but to go to secondary.