Often our bunnies' pee will look like it has white sediment in it, especially if it is dried up or has been deposited on cloth. The sediments stay behind on the cloth and the liquid runs through. If they are very thick, like if you feel them there is substance there, not just powder, then it would be a concern. Otherwise it is normal.
Since he did pee in an unusual spot, that is also a possible sign of urinary problems. Depending on how thick the chalky bit was, it can probably wait. Adding cranberry juice could certainly help but it is best to have a second bowl that contains a bit of cranberry in addition to a plain water bowl.