RY has stated that the Birth control isn't a magical serum, so magic wouldn't influence it.

Personally I never thought it was Bodhi since Imogens, Xadens and Violets PoVs all cross over. There is no way for Bodhi to be with both Xaden and Imogen.

The Onyx Storm es over Imogen right at the end of her chapter, and in Xadens, he mentions seeing her looking up at the sky.

I think Bodhi left with Xaden and Garrick because Xaden has a plan, and they are both his right-hand men. He needs them for something. He always planned on marrying Violet, its littered throughout the book.

My theory on the one who turned is Brennan and there's a ton of reasoning too.

As Alisha has said, Brennan doesn't have to be missing to be the one who turned. Plus, Brennan has amber coloured eyes, which could make could the red circles harder to notice. Violet constantly mentions how Xadens gold flecks have become amber. (Another hint).

He wasn't far from the battle either, so he could have gotten there. He almost burned out saving Mira (plus nearly losing her) and he was trying to save Teine. (I have multiple other reasons too)

But as for Imogens pov, I think it's partly to mislead us and have us thinking its Bodhi or Garrick. But they couldn't be in 2 places at the same time. Imogens pov ends with the Onyx storm coming over the city and Xaden mentions seeing her looking up at the sky.

Which would place Bodhi and Garrick in Draithus the whole time Xaden is in the Canyon with his new brother.