IF in doubt yoy should really go to the vet and get him checked, bladder sludge is very painful for a bunny

Another thought is that rabbits do not have the same pee consistency as other animals, especially if they are using it to mark things and in some situations it is entirely normal to pass calcium through it – so you can get chalky pee, or high sediment pee, this is not the same as bladder sludge, which is a far more serious version

http://wabbitwiki.com/wiki/Bladder_sludge_and_stones

This page might be of some use to you!

DFace has given you a good link, here’s another one with pictures of both sludge and normal pee with chalky residue:
http://www.medirabbit.com/EN/Uro_gen_diseases/generalities/Sludge.htm

It is normal for rabbits to expel surplus calcium via the kidneys. It’s a peculiarity of the specis – most other mammals get rid of excess calcium with the feces. If your bun has chalky pee often, so chalky that it resembles paint when it dries, you should see over his diet. The food he is getting sounds good, but all buns are different and parsley is a high calcium veg. It could perhaps be rotated with cilantro or dill.

Dittoing what the others have said. You could try rotating the parsley with other vegetables and observe if the pee is still chalky. Alfie’s system might’ve been able to take all the extra calcium when he was younger but since he’s a year old now, there may be an excess that he flushes out through the pee.