Black Rock Coriander & Orange Witbier to All grain

Hi all, 

I brewed a long time ago not a lot of success. Just recently started again, first with kits to get started and more recently I purchased a Grainfather and have had great results so far.

One kit I brewed which I really liked as something a little different to my usual go-to beer styles was the Black Rock Coriander & Orange Witbier. I used the kit can + a can of their wheat malt and ditched the standard yeast that cake with the kit and used Mangrove Jacks M20 Bavarian Wheat Yeast.

I'm looking for an all grain recipe for the same kind of deal with the orange and coriander additions and haven't yet come across any recipes that  thought might do this. 

Anyone who's brewed or tasted this Black Rock beer have an all grain recipe or even a starting point for something similar?

Or even if you haven't tasted this beer, any recommendations?

I'm not sure whether the orange and coriander should be added late in the boil or almost as a dry hop during or late in fermentation or post-fermentation?

As a side note, one thing I could definitely fault the kit on is very poor head retention.