I had the same problem with a pot of [URL="http://40kaddict.blogspot.co.uk/2013/03/nids-part-75-winged-hive-tyrant-and.html"]Seraphim Sepia on my Hive Tyrant[/URL]
But the pot I'd used before had no such problems. Even with a healthy shake follwoing my investigations it didn't solve the problem and it does appaear as if by magic. One minute it's perfect and still wet then you look again and it's dry with a 'flour' residue. I switched to Army Painter shades insetad, they're exactly the same as the old Badab Black, Gryphone Sepia and Devlan Mud washes, you can use as much as you want and they're cheaper too.
I'm sure you could probably use this result as some kind of 'effect in some way but not sure how you can fix your model. I'd be confident a an army painter wash might mitigate the problem, it essentially stains the residue the new colour, it's how I fixed mine. However, it may be too dark for your Blood Angels, good luck fixing it, I feel your pain.